the present condition of organic nature lecture i. (of vi.), "lectures to working men", at the museum of practical geology, 1863, on darwin's work: "origin of species". by thomas h. huxley editor's note of the great thinkers of the nineteenth century, thomas henry huxley, son of an ealing schoolmaster, was undoubtedly the most noteworthy. his researches in biology, his contributions to scientific controversy, his pungent criticisms of conventional beliefs and thoughts have probably had greater influence than the work of any other english scientist. and yet he was a "self-made" intellectualist. in spite of the fact that his father was a schoolmaster he passed through no regular course of education. "i had," he said, "two years of a pandemonium of a school (between eight and ten) and after that neither help nor sympathy in any intellectual direction till i reached manhood." when he was twelve a craving for reading found satisfaction in hutton's "geology," and when fifteen in hamilton's "logic." at seventeen huxley entered as a student at charing cross hospital, and three years later he was m.b. and the possessor of the gold medal for anatomy and physiology. an appointment as surgeon in the navy proved to be the entry to huxley's great scientific career, for he was gazetted to the "rattlesnake", commissioned for surveying work in torres straits. he was attracted by the teeming surface life of tropical seas and his study of it was the commencement of that revolution in scientific knowledge ultimately brought about by his researches. thomas henry huxley was born at ealing on may 4, 1825, and died at eastbourne june 29, 1895. lectures and essays by t.h. huxley on our knowledge of the causes of the phenomena of organic nature notice to the first edition. the publisher of these interesting lectures, having made an arrangement for their publication with mr. j. a. mays, the reporter, begs to append the following note from professor huxley:-"mr. j. aldous mays, who is taking shorthand notes of my 'lectures to working men,' has asked me to allow him, on his own account, to print those notes for the use of my audience. i willingly accede to this request, on the understanding that a notice is prefixed to the effect that i have no leisure to revise the lectures, or to make alterations in them, beyond the correction of any important error in a matter of fact." the present condition of organic nature. when it was my duty to consider what subject i would select for the six lectures [*to working men, at the museum of practical geology, 1863.] which i shall now have the pleasure of delivering to you, it occurred to me that i could not do better than endeavour to put before you in a true light, or in what i might perhaps with more modesty call, that which i conceive myself to be the true light, the position of a book which has been more praised and more abused, perhaps, than any book which has appeared for some years;--i mean mr. darwin's work on the "origin of species". that work, i doubt not, many of you have read; for i know the inquiring spirit which is rife among you. at any rate, all of you will have heard of it,--some by one kind of report and some by another kind of report; the attention of all and the curiosity of all have been probably more or less excited on the subject of that work. all i can do, and all i shall attempt to do, is to put before you that kind of judgment which has been formed by a man, who, of course, is liable to judge erroneously; but, at any rate, of one whose business and profession it is to form judgments upon questions of this nature. and here, as it will always happen when dealing with an extensive subject, the greater part of my course--if, indeed, so small a number of lectures can be properly called a course--must be devoted to preliminary matters, or rather to a statement of those facts and of those principles which the work itself dwells upon, and brings more or less directly before us. i have no right to suppose that all or any of you are naturalists; and even if you were, the misconceptions and misunderstandings prevalent even among naturalists on these matters would make it desirable that i should take the course i now propose to take,--that i should start from the beginning,--that i should endeavour to point out what is the existing state of the organic world,--that i should point out its past condition,--that i should state what is the precise nature of the undertaking which mr. darwin has taken in hand; that i should endeavour to show you what are the only methods by which that undertaking can be brought to an issue, and to point out to you how far the author of the work in question has satisfied those conditions, how far he has not satisfied them, how far they are satisfiable by man, and how far they are not satisfiable by man. to-night, in taking up the first part of this question, i shall endeavour to put before you a sort of broad notion of our knowledge of the condition of the living world. there are many ways of doing this. i might deal with it pictorially and graphically. following the example of humboldt in his "aspects of nature", i might endeavour to point out the infinite variety of organic life in every mode of its existence, with reference to the variations of climate and the like; and such an attempt would be fraught with interest to us all; but considering the subject before us, such a course would not be that best calculated to assist us. in an argument of this kind we must go further and dig deeper into the matter; we must endeavour to look into the foundations of living nature, if i may so say, and discover the principles involved in some of her most secret operations. i propose, therefore, in the first place, to take some ordinary animal with which you are all familiar, and, by easily comprehensible and obvious examples drawn from it, to show what are the kind of problems which living beings in general lay before us; and i shall then show you that the same problems are laid open to us by all kinds of living beings. but first, let me say in what sense i have used the words "organic nature." in speaking of the causes which lead to our present knowledge of organic nature, i have used it almost as an equivalent of the word "living," and for this reason,--that in almost all living beings you can distinguish several distinct portions set apart to do particular things and work in a particular way. these are termed "organs," and the whole together is called "organic." and as it is universally characteristic of them, this term "organic" has been very conveniently employed to denote the whole of living nature,--the whole of the plant world, and the whole of the animal world. few animals can be more familiar to you than that whose skeleton is shown on our diagram. you need not bother yourselves with this "equus caballus" written under it; that is only the latin name of it, and does not make it any better. it simply means the common horse. suppose we wish to understand all about the horse. our first object must be to study the structure of the animal. the whole of his body is inclosed within a hide, a skin covered with hair; and if that hide or skin be taken off, we find a great mass of flesh, or what is technically called muscle, being the substance which by its power of contraction enables the animal to move. these muscles move the hard parts one upon the other, and so give that strength and power of motion which renders the horse so useful to us in the performance of those services in which we employ him. and then, on separating and removing the whole of this skin and flesh, you have a great series of bones, hard structures, bound together with ligaments, and forming the skeleton which is represented here. [illustration: figure 1. (section through a horse.)] [illustration: figure 2. (section through a cell.)] in that skeleton there are a number of parts to be recognized. the long series of bones, beginning from the skull and ending in the tail, is called the spine, and those in front are the ribs; and then there are two pairs of limbs, one before and one behind; and there are what we all know as the fore-legs and the hind-legs. if we pursue our researches into the interior of this animal, we find within the framework of the skeleton a great cavity, or rather, i should say, two great cavities,--one cavity beginning in the skull and running through the neck-bones, along the spine, and ending in the tail, containing the brain and the spinal marrow, which are extremely important organs. the second great cavity, commencing with the mouth, contains the gullet, the stomach, the long intestine, and all the rest of those internal apparatus which are essential for digestion; and then in the same great cavity, there are lodged the heart and all the great vessels going from it; and, besides that, the organs of respiration--the lungs: and then the kidneys, and the organs of reproduction, and so on. let us now endeavour to reduce this notion of a horse that we now have, to some such kind of simple expression as can be at once, and without difficulty, retained in the mind, apart from all minor details. if i make a transverse section, that is, if i were to saw a dead horse across, i should find that, if i left out the details, and supposing i took my section through the anterior region, and through the fore-limbs, i should have here this kind of section of the body (fig. 1). here would be the upper part of the animal--that great mass of bones that we spoke of as the spine (a, fig. 1). here i should have the alimentary canal (b, fig. 1). here i should have the heart (c, fig. 1); and then you see, there would be a kind of double tube, the whole being inclosed within the hide; the spinal marrow would be placed in the upper tube (a, fig. 1), and in the lower tube (d d, fig. 1), there would be the alimentary canal (b), and the heart (c); and here i shall have the legs proceeding from each side. for simplicity's sake, i represent them merely as stumps (e e, fig. 1). now that is a horse--as mathematicians would say--reduced to its most simple expression. carry that in your minds, if you please, as a simplified idea of the structure of the horse. the considerations which i have now put before you belong to what we technically call the 'anatomy' of the horse. now, suppose we go to work upon these several parts,--flesh and hair, and skin and bone, and lay open these various organs with our scalpels, and examine them by means of our magnifying-glasses, and see what we can make of them. we shall find that the flesh is made up of bundles of strong fibres. the brain and nerves, too, we shall find, are made up of fibres, and these queer-looking things that are called ganglionic corpuscles. if we take a slice of the bone and examine it, we shall find that it is very like this diagram of a section of the bone of an ostrich, though differing, of course, in some details; and if we take any part whatsoever of the tissue, and examine it, we shall find it all has a minute structure, visible only under the microscope. all these parts constitute microscopic anatomy or 'histology.' these parts are constantly being changed; every part is constantly growing, decaying, and being replaced during the life of the animal. the tissue is constantly replaced by new material; and if you go back to the young state of the tissue in the case of muscle, or in the case of skin, or any of the organs i have mentioned, you will find that they all come under the same condition. every one of these microscopic filaments and fibres (i now speak merely of the general character of the whole process)--every one of these parts--could be traced down to some modification of a tissue which can be readily divided into little particles of fleshy matter, of that substance which is composed of the chemical elements, carbon, hydrogen, oxygen, and nitrogen, having such a shape as this (fig. 2). these particles, into which all primitive tissues break up, are called cells. if i were to make a section of a piece of the skin of my hand, i should find that it was made up of these cells. if i examine the fibres which form the various organs of all living animals, i should find that all of them, at one time or other, had been formed out of a substance consisting of similar elements; so that you see, just as we reduced the whole body in the gross to that sort of simple expression given in fig. 1, so we may reduce the whole of the microscopic structural elements to a form of even greater simplicity; just as the plan of the whole body may be so represented in a sense (fig. 1), so the primary structure of every tissue may be represented by a mass of cells (fig. 2). having thus, in this sort of general way, sketched to you what i may call, perhaps, the architecture of the body of the horse (what we term technically its morphology), i must now turn to another aspect. a horse is not a mere dead structure: it is an active, living, working machine. hitherto we have, as it were, been looking at a steam-engine with the fires out, and nothing in the boiler; but the body of the living animal is a beautifully-formed active machine, and every part has its different work to do in the working of that machine, which is what we call its life. the horse, if you see him after his day's work is done, is cropping the grass in the fields, as it may be, or munching the oats in his stable. what is he doing? his jaws are working as a mill--and a very complex mill too--grinding the corn, or crushing the grass to a pulp. as soon as that operation has taken place, the food is passed down to the stomach, and there it is mixed with the chemical fluid called the gastric juice, a substance which has the peculiar property of making soluble and dissolving out the nutritious matter in the grass, and leaving behind those parts which are not nutritious; so that you have, first, the mill, then a sort of chemical digester; and then the food, thus partially dissolved, is carried back by the muscular contractions of the intestines into the hinder parts of the body, while the soluble portions are taken up into the blood. the blood is contained in a vast system of pipes, spreading through the whole body, connected with a force pump,--the heart,--which, by its position and by the contractions of its valves, keeps the blood constantly circulating in one direction, never allowing it to rest; and then, by means of this circulation of the blood, laden as it is with the products of digestion, the skin, the flesh, the hair, and every other part of the body, draws from it that which it wants, and every one of these organs derives those materials which are necessary to enable it to do its work. the action of each of these organs, the performance of each of these various duties, involve in their operation a continual absorption of the matters necessary for their support, from the blood, and a constant formation of waste products, which are returned to the blood, and conveyed by it to the lungs and the kidneys, which are organs that have allotted to them the office of extracting, separating, and getting rid of these waste products; and thus the general nourishment, labour, and repair of the whole machine is kept up with order and regularity. but not only is it a machine which feeds and appropriates to its own support the nourishment necessary to its existence--it is an engine for locomotive purposes. the horse desires to go from one place to another; and to enable it to do this, it has those strong contractile bundles of muscles attached to the bones of its limbs, which are put in motion by means of a sort of telegraphic apparatus formed by the brain and the great spinal cord running through the spine or backbone; and to this spinal cord are attached a number of fibres termed nerves, which proceed to all parts of the structure. by means of these the eyes, nose, tongue, and skin--all the organs of perception--transmit impressions or sensations to the brain, which acts as a sort of great central telegraph-office, receiving impressions and sending messages to all parts of the body, and putting in motion the muscles necessary to accomplish any movement that may be desired. so that you have here an extremely complex and beautifully-proportioned machine, with all its parts working harmoniously together towards one common object--the preservation of the life of the animal. now, note this: the horse makes up its waste by feeding, and its food is grass or oats, or perhaps other vegetable products; therefore, in the long run, the source of all this complex machinery lies in the vegetable kingdom. but where does the grass, or the oat, or any other plant, obtain this nourishing food-producing material? at first it is a little seed, which soon begins to draw into itself from the earth and the surrounding air matters which in themselves contain no vital properties whatever; it absorbs into its own substance water, an inorganic body; it draws into its substance carbonic acid, an inorganic matter; and ammonia, another inorganic matter, found in the air; and then, by some wonderful chemical process, the details of which chemists do not yet understand, though they are near foreshadowing them, it combines them into one substance, which is known to us as 'protein,' a complex compound of carbon, hydrogen, oxygen, and nitrogen, which alone possesses the property of manifesting vitality and of permanently supporting animal life. so that, you see, the waste products of the animal economy, the effete materials which are continually being thrown off by all living beings, in the form of organic matters, are constantly replaced by supplies of the necessary repairing and rebuilding materials drawn from the plants, which in their turn manufacture them, so to speak, by a mysterious combination of those same inorganic materials. let us trace out the history of the horse in another direction. after a certain time, as the result of sickness or disease, the effect of accident, or the consequence of old age, sooner or later, the animal dies. the multitudinous operations of this beautiful mechanism flag in their performance, the horse loses its vigour, and after passing through the curious series of changes comprised in its formation and preservation, it finally decays, and ends its life by going back into that inorganic world from which all but an inappreciable fraction of its substance was derived. its bones become mere carbonate and phosphate of lime; the matter of its flesh, and of its other parts, becomes, in the long run, converted into carbonic acid, into water, and into ammonia. you will now, perhaps, understand the curious relation of the animal with the plant, of the organic with the inorganic world, which is shown in this diagram (fig. 3). [illustration: figure 3. (diagram showing material relationship of the vegetable, animal and inorganic worlds.)] the plant gathers these inorganic materials together and makes them up into its own substance. the animal eats the plant and appropriates the nutritious portions to its own sustenance, rejects and gets rid of the useless matters; and, finally, the animal itself dies, and its whole body is decomposed and returned into the inorganic world. there is thus a constant circulation from one to the other, a continual formation of organic life from inorganic matters, and as constant a return of the matter of living bodies to the inorganic world; so that the materials of which our bodies are composed are largely, in all probability, the substances which constituted the matter of long extinct creations, but which have in the interval constituted a part of the inorganic world. thus we come to the conclusion, strange at first sight, that the matter constituting the living world is identical with that which forms the inorganic world. and not less true is it that, remarkable as are the powers or, in other words, as are the forces which are exerted by living beings, yet all these forces are either identical with those which exist in the inorganic world, or they are convertible into them; i mean in just the same sense as the researches of physical philosophers have shown that heat is convertible into electricity, that electricity is convertible into magnetism, magnetism into mechanical force or chemical force, and any one of them with the other, each being measurable in terms of the other,--even so, i say, that great law is applicable to the living world. consider why is the skeleton of this horse capable of supporting the masses of flesh and the various organs forming the living body, unless it is because of the action of the same forces of cohesion which combines together the particles of matter composing this piece of chalk? what is there in the muscular contractile power of the animal but the force which is expressible, and which is in a certain sense convertible, into the force of gravity which it overcomes? or, if you go to more hidden processes, in what does the process of digestion differ from those processes which are carried on in the laboratory of the chemist? even if we take the most recondite and most complex operations of animal life--those of the nervous system, these of late years have been shown to be--i do not say identical in any sense with the electrical processes--but this has been shown, that they are in some way or other associated with them; that is to say, that every amount of nervous action is accompanied by a certain amount of electrical disturbance in the particles of the nerves in which that nervous action is carried on. in this way the nervous action is related to electricity in the same way that heat is related to electricity; and the same sort of argument which demonstrates the two latter to be related to one another shows that the nervous forces are correlated to electricity; for the experiments of m. dubois reymond and others have shown that whenever a nerve is in a state of excitement, sending a message to the muscles or conveying an impression to the brain, there is a disturbance of the electrical condition of that nerve which does not exist at other times; and there are a number of other facts and phenomena of that sort; so that we come to the broad conclusion that not only as to living matter itself, but as to the forces that matter exerts, there is a close relationship between the organic and the inorganic world--the difference between them arising from the diverse combination and disposition of identical forces, and not from any primary diversity, so far as we can see. i said just now that the horse eventually died and became converted into the same inorganic substances from whence all but an inappreciable fraction of its substance demonstrably originated, so that the actual wanderings of matter are as remarkable as the transmigrations of the soul fabled by indian tradition. but before death has occurred, in the one sex or the other, and in fact in both, certain products or parts of the organism have been set free, certain parts of the organisms of the two sexes have come into contact with one another, and from that conjunction, from that union which then takes place, there results the formation of a new being. at stated times the mare, from a particular part of the interior of her body, called the ovary, gets rid of a minute particle of matter comparable in all essential respects with that which we called a cell a little while since, which cell contains a kind of nucleus in its centre, surrounded by a clear space and by a viscid mass of protein substance (fig. 2); and though it is different in appearance from the eggs which we are mostly acquainted with, it is really an egg. after a time this minute particle of matter, which may only be a small fraction of a grain in weight, undergoes a series of changes,--wonderful, complex changes. finally, upon its surface there is fashioned a little elevation, which afterwards becomes divided and marked by a groove. the lateral boundaries of the groove extend upwards and downwards, and at length give rise to a double tube. in the upper smaller tube the spinal marrow and brain are fashioned; in the lower, the alimentary canal and heart; and at length two pairs of buds shoot out at the sides of the body, which are the rudiments of the limbs. in fact a true drawing of a section of the embryo in this state would in all essential respects resemble that diagram of a horse reduced to its simplest expression, which i first placed before you (fig. 1). slowly and gradually these changes take place. the whole of the body, at first, can be broken up into "cells," which become in one place metamorphosed into muscle,--in another place into gristle and bone,--in another place into fibrous tissue,--and in another into hair; every part becoming gradually and slowly fashioned, as if there were an artificer at work in each of these complex structures that we have mentioned. this embryo, as it is called, then passes into other conditions. i should tell you that there is a time when the embryos of neither dog, nor horse, nor porpoise, nor monkey, nor man, can be distinguished by any essential feature one from the other; there is a time when they each and all of them resemble this one of the dog. but as development advances, all the parts acquire their speciality, till at length you have the embryo converted into the form of the parent from which it started. so that you see, this living animal, this horse, begins its existence as a minute particle of nitrogenous matter, which, being supplied with nutriment (derived, as i have shown, from the inorganic world), grows up according to the special type and construction of its parents, works and undergoes a constant waste, and that waste is made good by nutriment derived from the inorganic world; the waste given off in this way being directly added to the inorganic world; and eventually the animal itself dies, and, by the process of decomposition, its whole body is returned to those conditions of inorganic matter in which its substance originated. this, then, is that which is true of every living form, from the lowest plant to the highest animal--to man himself. you might define the life of every one in exactly the same terms as those which i have now used; the difference between the highest and the lowest being simply in the complexity of the developmental changes, the variety of the structural forms, the diversity of the physiological functions which are exerted by each. if i were to take an oak tree as a specimen of the plant world, i should find that it originated in an acorn, which, too, commenced in a cell; the acorn is placed in the ground, and it very speedily begins to absorb the inorganic matters i have named, adds enormously to its bulk, and we can see it, year after year, extending itself upward and downward, attracting and appropriating to itself inorganic materials, which it vivifies, and eventually, as it ripens, gives off its own proper acorns, which again run the same course. but i need not multiply examples,--from the highest to the lowest the essential features of life are the same, as i have described in each of these cases. so much, then, for these particular features of the organic world, which you can understand and comprehend, so long as you confine yourself to one sort of living being, and study that only. but, as you know, horses are not the only living creatures in the world; and again, horses, like all other animals, have certain limits--are confined to a certain area on the surface of the earth on which we live,--and, as that is the simpler matter, i may take that first. in its wild state, and before the discovery of america, when the natural state of things was interfered with by the spaniards, the horse was only to be found in parts of the earth which are known to geographers as the old world; that is to say, you might meet with horses in europe, asia, or africa; but there were none in australia, and there were none whatsoever in the whole continent of america, from labrador down to cape horn. this is an empirical fact, and it is what is called, stated in the way i have given it you, the 'geographical distribution' of the horse. why horses should be found in europe, asia, and africa, and not in america, is not obvious; the explanation that the conditions of life in america are unfavourable to their existence, and that, therefore, they had not been created there, evidently does not apply; for when the invading spaniards, or our own yeomen farmers, conveyed horses to these countries for their own use, they were found to thrive well and multiply very rapidly; and many are even now running wild in those countries, and in a perfectly natural condition. now, suppose we were to do for every animal what we have here done for the horse,--that is, to mark off and distinguish the particular district or region to which each belonged; and supposing we tabulated all these results, that would be called the geographical distribution of animals, while a corresponding study of plants would yield as a result the geographical distribution of plants. i pass on from that now, as i merely wished to explain to you what i meant by the use of the term 'geographical distribution.' as i said, there is another aspect, and a much more important one, and that is, the relations of the various animals to one another. the horse is a very well-defined matter-of-fact sort of animal, and we are all pretty familiar with its structure. i dare say it may have struck you, that it resembles very much no other member of the animal kingdom, except perhaps the zebra or the ass. but let me ask you to look along these diagrams. here is the skeleton of the horse, and here the skeleton of the dog. you will notice that we have in the horse a skull, a backbone and ribs, shoulder-blades and haunch-bones. in the fore-limb, one upper arm-bone, two fore arm-bones, wrist-bones (wrongly called knee), and middle hand-bones, ending in the three bones of a finger, the last of which is sheathed in the horny hoof of the fore-foot: in the hind-limb, one thigh-bone, two leg-bones, anklebones, and middle foot-bones, ending in the three bones of a toe, the last of which is encased in the hoof of the hind-foot. now turn to the dog's skeleton. we find identically the same bones, but more of them, there being more toes in each foot, and hence more toe-bones. well, that is a very curious thing! the fact is that the dog and the horse--when one gets a look at them without the outward impediments of the skin--are found to be made in very much the same sort of fashion. and if i were to make a transverse section of the dog, i should find the same organs that i have already shown you as forming parts of the horse. well, here is another skeleton--that of a kind of lemur--you see he has just the same bones; and if i were to make a transverse section of it, it would be just the same again. in your mind's eye turn him round, so as to put his backbone in a position inclined obliquely upwards and forwards, just as in the next three diagrams, which represent the skeletons of an orang, a chimpanzee, a gorilla, and you find you have no trouble in identifying the bones throughout; and lastly turn to the end of the series, the diagram representing a man's skeleton, and still you find no great structural feature essentially altered. there are the same bones in the same relations. from the horse we pass on and on, with gradual steps, until we arrive at last at the highest known forms. on the other hand, take the other line of diagrams, and pass from the horse downwards in the scale to this fish; and still, though the modifications are vastly greater, the essential framework of the organization remains unchanged. here, for instance, is a porpoise: here is its strong backbone, with the cavity running through it, which contains the spinal cord; here are the ribs, here the shoulder blade; here is the little short upper-arm bone, here are the two forearm bones, the wrist-bone, and the finger-bones. strange, is it not, that the porpoise should have in this queer-looking affair--its flapper (as it is called), the same fundamental elements as the fore-leg of the horse or the dog, or the ape or man; and here you will notice a very curious thing,--the hinder limbs are absent. now, let us make another jump. let us go to the codfish: here you see is the forearm, in this large pectoral fin--carrying your mind's eye onward from the flapper of the porpoise. and here you have the hinder limbs restored in the shape of these ventral fins. if i were to make a transverse section of this, i should find just the same organs that we have before noticed. so that, you see, there comes out this strange conclusion as the result of our investigations, that the horse, when examined and compared with other animals, is found by no means to stand alone in nature; but that there are an enormous number of other creatures which have backbones, ribs, and legs, and other parts arranged in the same general manner, and in all their formation exhibiting the same broad peculiarities. i am sure that you cannot have followed me even in this extremely elementary exposition of the structural relations of animals, without seeing what i have been driving at all through, which is, to show you that, step by step, naturalists have come to the idea of a unity of plan, or conformity of construction, among animals which appeared at first sight to be extremely dissimilar. and here you have evidence of such a unity of plan among all the animals which have backbones, and which we technically call "vertebrata". but there are multitudes of other animals, such as crabs, lobsters, spiders, and so on, which we term "annulosa". in these i could not point out to you the parts that correspond with those of the horse,--the backbone, for instance,--as they are constructed upon a very different principle, which is also common to all of them; that is to say, the lobster, the spider, and the centipede, have a common plan running through their whole arrangement, in just the same way that the horse, the dog, and the porpoise assimilate to each other. yet other creatures--whelks, cuttlefishes, oysters, snails, and all their tribe ("mollusca")--resemble one another in the same way, but differ from both "vertebrata" and "annulosa"; and the like is true of the animals called "coelenterata" (polypes) and "protozoa" (animalcules and sponges). now, by pursuing this sort of comparison, naturalists have arrived at the conviction that there are,--some think five, and some seven,--but certainly not more than the latter number--and perhaps it is simpler to assume five--distinct plans or constructions in the whole of the animal world; and that the hundreds of thousands of species of creatures on the surface of the earth, are all reducible to those five, or, at most, seven, plans of organization. but can we go no further than that? when one has got so far, one is tempted to go on a step and inquire whether we cannot go back yet further and bring down the whole to modifications of one primordial unit. the anatomist cannot do this; but if he call to his aid the study of development, he can do it. for we shall find that, distinct as those plans are, whether it be a porpoise or man, or lobster, or any of those other kinds i have mentioned, every one begins its existence with one and the same primitive form,--that of the egg, consisting, as we have seen, of a nitrogenous substance, having a small particle or nucleus in the centre of it. furthermore, the earlier changes of each are substantially the same. and it is in this that lies that true "unity of organization" of the animal kingdom which has been guessed at and fancied for many years; but which it has been left to the present time to be demonstrated by the careful study of development. but is it possible to go another step further still, and to show that in the same way the whole of the organic world is reducible to one primitive condition of form? is there among the plants the same primitive form of organization, and is that identical with that of the animal kingdom? the reply to that question, too, is not uncertain or doubtful. it is now proved that every plant begins its existence under the same form; that is to say, in that of a cell--a particle of nitrogenous matter having substantially the same conditions. so that if you trace back the oak to its first germ, or a man, or a horse, or lobster, or oyster, or any other animal you choose to name, you shall find each and all of these commencing their existence in forms essentially similar to each other: and, furthermore, that the first processes of growth, and many of the subsequent modifications, are essentially the same in principle in almost all. in conclusion, let me, in a few words, recapitulate the positions which i have laid down. and you must understand that i have not been talking mere theory; i have been speaking of matters which are as plainly demonstrable as the commonest propositions of euclid--of facts that must form the basis of all speculations and beliefs in biological science. we have gradually traced down all organic forms, or, in other words, we have analyzed the present condition of animated nature, until we found that each species took its origin in a form similar to that under which all the others commence their existence. we have found the whole of the vast array of living forms, with which we are surrounded, constantly growing, increasing, decaying and disappearing; the animal constantly attracting, modifying, and applying to its sustenance the matter of the vegetable kingdom, which derived its support from the absorption and conversion of inorganic matter. and so constant and universal is this absorption, waste, and reproduction, that it may be said with perfect certainty that there is left in no one of our bodies at the present moment a millionth part of the matter of which they were originally formed! we have seen, again, that not only is the living matter derived from the inorganic world, but that the forces of that matter are all of them correlative with and convertible into those of inorganic nature. this, for our present purposes, is the best view of the present condition of organic nature which i can lay before you: it gives you the great outlines of a vast picture, which you must fill up by your own study. in the next lecture i shall endeavour in the same way to go back into the past, and to sketch in the same broad manner the history of life in epochs preceding our own. a critical examination of the position of mr. darwin's work, "on the origin of species," in relation to the complete theory of the causes of the phenomena of organic nature by thomas h. huxley in the preceding five lectures i have endeavoured to give you an account of those facts, and of those reasonings from facts, which form the data upon which all theories regarding the causes of the phenomena of organic nature must be based. and, although i have had frequent occasion to quote mr. darwin--as all persons hereafter, in speaking upon these subjects, will have occasion to quote his famous book on the "origin of species,"--you must yet remember that, wherever i have quoted him, it has not been upon theoretical points, or for statements in any way connected with his particular speculations, but on matters of fact, brought forward by himself, or collected by himself, and which appear incidentally in his book. if a man 'will' make a book, professing to discuss a single question, an encyclopaedia, i cannot help it. now, having had an opportunity of considering in this sort of way the different statements bearing upon all theories whatsoever, i have to lay before you, as fairly as i can, what is mr. darwin's view of the matter and what position his theories hold, when judged by the principles which i have previously laid down, as deciding our judgments upon all theories and hypotheses. i have already stated to you that the inquiry respecting the causes of the phenomena of organic nature resolves itself into two problems--the first being the question of the origination of living or organic beings; and the second being the totally distinct problem of the modification and perpetuation of organic beings when they have already come into existence. the first question mr. darwin does not touch; he does not deal with it at all; but he says--given the origin of organic matter--supposing its creation to have already taken place, my object is to show in consequence of what laws and what demonstrable properties of organic matter, and of its environments, such states of organic nature as those with which we are acquainted must have come about. this, you will observe, is a perfectly legitimate proposition; every person has a right to define the limits of the inquiry which he sets before himself; and yet it is a most singular thing that in all the multifarious, and, not unfrequently, ignorant attacks which have been made upon the 'origin of species', there is nothing which has been more speciously criticised than this particular limitation. if people have nothing else to urge against the book, they say--"well, after all, you see, mr. darwin's explanation of the 'origin of species' is not good for much, because, in the long run, he admits that he does not know how organic matter began to exist. but if you admit any special creation for the first particle of organic matter you may just as well admit it for all the rest; five hundred or five thousand distinct creations are just as intelligible, and just as little difficult to understand, as one." the answer to these cavils is two-fold. in the first place, all human inquiry must stop somewhere; all our knowledge and all our investigation cannot take us beyond the limits set by the finite and restricted character of our faculties, or destroy the endless unknown, which accompanies, like its shadow, the endless procession of phenomena. so far as i can venture to offer an opinion on such a matter, the purpose of our being in existence, the highest object that human beings can set before themselves, is not the pursuit of any such chimera as the annihilation of the unknown; but it is simply the unwearied endeavour to remove its boundaries a little further from our little sphere of action. i wonder if any historian would for a moment admit the objection, that it is preposterous to trouble ourselves about the history of the roman empire, because we do not know anything positive about the origin and first building of the city of rome! would it be a fair objection to urge, respecting the sublime discoveries of a newton, or a kepler, those great philosophers, whose discoveries have been of the profoundest benefit and service to all men,--to say to them--"after all that you have told us as to how the planets revolve, and how they are maintained in their orbits, you cannot tell us what is the cause of the origin of the sun, moon, and stars. so what is the use of what you have done?" yet these objections would not be one whit more preposterous than the objections which have been made to the 'origin of species.' mr. darwin, then, had a perfect right to limit his inquiry as he pleased, and the only question for us--the inquiry being so limited--is to ascertain whether the method of his inquiry is sound or unsound; whether he has obeyed the canons which must guide and govern all investigation, or whether he has broken them; and it was because our inquiry this evening is essentially limited to that question, that i spent a good deal of time in a former lecture (which, perhaps, some of you thought might have been better employed), in endeavouring to illustrate the method and nature of scientific inquiry in general. we shall now have to put in practice the principles that i then laid down. i stated to you in substance, if not in words, that wherever there are complex masses of phenomena to be inquired into, whether they be phenomena of the affairs of daily life, or whether they belong to the more abstruse and difficult problems laid before the philosopher, our course of proceeding in unravelling that complex chain of phenomena with a view to get at its cause, is always the same; in all cases we must invent an hypothesis; we must place before ourselves some more or less likely supposition respecting that cause; and then, having assumed an hypothesis, having supposed cause for the phenomena in question, we must endeavour, on the one hand, to demonstrate our hypothesis, or, on the other, to upset and reject it altogether, by testing it in three ways. we must, in the first place, be prepared to prove that the supposed causes of the phenomena exist in nature; that they are what the logicians call 'vera causae'--true causes;--in the next place, we should be prepared to show that the assumed causes of the phenomena are competent to produce such phenomena as those which we wish to explain by them; and in the last place, we ought to be able to show that no other known causes are competent to produce those phenomena. if we can succeed in satisfying these three conditions we shall have demonstrated our hypothesis; or rather i ought to say we shall have proved it as far as certainty is possible for us; for, after all, there is no one of our surest convictions which may not be upset, or at any rate modified by a further accession of knowledge. it was because it satisfied these conditions that we accepted the hypothesis as to the disappearance of the tea-pot and spoons in the case i supposed in a previous lecture; we found that our hypothesis on that subject was tenable and valid, because the supposed cause existed in nature, because it was competent to account for the phenomena, and because no other known cause was competent to account for them; and it is upon similar grounds that any hypothesis you choose to name is accepted in science as tenable and valid. what is mr. darwin's hypothesis? as i apprehend it--for i have put it into a shape more convenient for common purposes than i could find 'verbatim' in his book--as i apprehend it, i say, it is, that all the phenomena of organic nature, past and present, result from, or are caused by, the inter-action of those properties of organic matter, which we have called atavism and variability, with the conditions of existence; or, in other words,--given the existence of organic matter, its tendency to transmit its properties, and its tendency occasionally to vary; and, lastly, given the conditions of existence by which organic matter is surrounded--that these put together are the causes of the present and of the past conditions of organic nature. such is the hypothesis as i understand it. now let us see how it will stand the various tests which i laid down just now. in the first place, do these supposed causes of the phenomena exist in nature? is it the fact that in nature these properties of organic matter--atavism and variability--and those phenomena which we have called the conditions of existence,--is it true that they exist? well, of course, if they do not exist, all that i have told you in the last three or four lectures must be incorrect, because i have been attempting to prove that they do exist, and i take it that there is abundant evidence that they do exist; so far, therefore, the hypothesis does not break down. but in the next place comes a much more difficult inquiry:--are the causes indicated competent to give rise to the phenomena of organic nature? i suspect that this is indubitable to a certain extent. it is demonstrable, i think, as i have endeavoured to show you, that they are perfectly competent to give rise to all the phenomena which are exhibited by races in nature. furthermore, i believe that they are quite competent to account for all that we may call purely structural phenomena which are exhibited by species in nature. on that point also i have already enlarged somewhat. again, i think that the causes assumed are competent to account for most of the physiological characteristics of species, and i not only think that they are competent to account for them, but i think that they account for many things which otherwise remain wholly unaccountable and inexplicable, and i may say incomprehensible. for a full exposition of the grounds on which this conviction is based, i must refer you to mr. darwin's work; all that i can do now is to illustrate what i have said by two or three cases taken almost at random. i drew your attention, on a previous evening, to the facts which are embodied in our systems of classification, which are the results of the examination and comparison of the different members of the animal kingdom one with another. i mentioned that the whole of the animal kingdom is divisible into five sub-kingdoms; that each of these sub-kingdoms is again divisible into provinces; that each province may be divided into classes, and the classes into the successively smaller groups, orders, families, genera, and species. now, in each of these groups, the resemblance in structure among the members of the group is closer in proportion as the group is smaller. thus, a man and a worm are members of the animal kingdom in virtue of certain apparently slight though really fundamental resemblances which they present. but a man and a fish are members of the same sub-kingdom 'vertebrata', because they are much more like one another than either of them is to a worm, or a snail, or any member of the other sub-kingdoms. for similar reasons men and horses are arranged as members of the same class, 'mammalia'; men and apes as members of the same order, 'primates'; and if there were any animals more like men than they were like any of the apes, and yet different from men in important and constant particulars of their organization, we should rank them as members of the same family, or of the same genus, but as of distinct species. that it is possible to arrange all the varied forms of animals into groups, having this sort of singular subordination one to the other, is a very remarkable circumstance; but, as mr. darwin remarks, this is a result which is quite to be expected, if the principles which he lays down be correct. take the case of the races which are known to be produced by the operation of atavism and variability, and the conditions of existence which check and modify these tendencies. take the case of the pigeons that i brought before you; there it was shown that they might be all classed as belonging to some one of five principal divisions, and that within these divisions other subordinate groups might be formed. the members of these groups are related to one another in just the same way as the genera of a family, and the groups themselves as the families of an order, or the orders of a class; while all have the same sort of structural relations with the wild rock-pigeon, as the members of any great natural group have with a real or imaginary typical form. now, we know that all varieties of pigeons of every kind have arisen by a process of selective breeding from a common stock, the rock-pigeon; hence, you see, that if all species of animals have proceeded from some common stock, the general character of their structural relations, and of our systems of classification, which express those relations, would be just what we find them to be. in other words, the hypothetical cause is, so far, competent to produce effects similar to those of the real cause. take, again, another set of very remarkable facts,--the existence of what are called rudimentary organs, organs for which we can find no obvious use, in the particular animal economy in which they are found, and yet which are there. such are the splint-like bones in the leg of the horse, which i here show you, and which correspond with bones which belong to certain toes and fingers in the human hand and foot. in the horse you see they are quite rudimentary, and bear neither toes nor fingers; so that the horse has only one "finger" in his fore-foot and one "toe" in his hind foot. but it is a very curious thing that the animals closely allied to the horse show more toes than he; as the rhinoceros, for instance: he has these extra toes well formed, and anatomical facts show very clearly that he is very closely related to the horse indeed. so we may say that animals, in an anatomical sense nearly related to the horse, have those parts which are rudimentary in him, fully developed. again, the sheep and the cow have no cutting-teeth, but only a hard pad in the upper jaw. that is the common characteristic of ruminants in general. but the calf has in its upper jaw some rudiments of teeth which never are developed, and never play the part of teeth at all. well, if you go back in time, you find some of the older, now extinct, allies of the ruminants have well-developed teeth in their upper jaws; and at the present day the pig (which is in structure closely connected with ruminants) has well-developed teeth in its upper jaw; so that here is another instance of organs well-developed and very useful, in one animal, represented by rudimentary organs, for which we can discover no purpose whatsoever, in another closely allied animal. the whalebone whale, again, has horny "whalebone" plates in its mouth, and no teeth; but the young foetal whale, before it is born, has teeth in its jaws; they, however, are never used, and they never come to anything. but other members of the group to which the whale belongs have well-developed teeth in both jaws. upon any hypothesis of special creation, facts of this kind appear to me to be entirely unaccountable and inexplicable, but they cease to be so if you accept mr. darwin's hypothesis, and see reason for believing that the whalebone whale and the whale with teeth in its mouth both sprang from a whale that had teeth, and that the teeth of the foetal whale are merely remnants--recollections, if we may so say--of the extinct whale. so in the case of the horse and the rhinoceros: suppose that both have descended by modification from some earlier form which had the normal number of toes, and the persistence of the rudimentary bones which no longer support toes in the horse becomes comprehensible. in the language that we speak in england, and in the language of the greeks, there are identical verbal roots, or elements entering into the composition of words. that fact remains unintelligible so long as we suppose english and greek to be independently created tongues; but when it is shown that both languages are descended from one original, the sanscrit, we give an explanation of that resemblance. in the same way the existence of identical structural roots, if i may so term them, entering into the composition of widely different animals, is striking evidence in favour of the descent of those animals from a common original. to turn to another kind of illustration:--if you regard the whole series of stratified rocks--that enormous thickness of sixty or seventy thousand feet that i have mentioned before, constituting the only record we have of a most prodigious lapse of time, that time being, in all probability, but a fraction of that of which we have no record;--if you observe in these successive strata of rocks successive groups of animals arising and dying out, a constant succession, giving you the same kind of impression, as you travel from one group of strata to another, as you would have in travelling from one country to another;--when you find this constant succession of forms, their traces obliterated except to the man of science,--when you look at this wonderful history, and ask what it means, it is only a paltering with words if you are offered the reply,--'they were so created.' but if, on the other hand, you look on all forms of organized beings as the results of the gradual modification of a primitive type, the facts receive a meaning, and you see that these older conditions are the necessary predecessors of the present. viewed in this light the facts of palaeontology receive a meaning--upon any other hypothesis, i am unable to see, in the slightest degree, what knowledge or signification we are to draw out of them. again, note as bearing upon the same point, the singular likeness which obtains between the successive faunae and florae, whose remains are preserved on the rocks: you never find any great and enormous difference between the immediately successive faunae and florae, unless you have reason to believe there has also been a great lapse of time or a great change of conditions. the animals, for instance, of the newest tertiary rocks, in any part of the world, are always, and without exception, found to be closely allied with those which now live in that part of the world. for example, in europe, asia, and africa, the large mammals are at present rhinoceroses, hippopotamuses, elephants, lions, tigers, oxen, horses, etc.; and if you examine the newest tertiary deposits, which contain the animals and plants which immediately preceded those which now exist in the same country, you do not find gigantic specimens of ant-eaters and kangaroos, but you find rhinoceroses, elephants, lions, tigers, etc.,--of different species to those now living,--but still their close allies. if you turn to south america, where, at the present day, we have great sloths and armadilloes and creatures of that kind, what do you find in the newest tertiaries? you find the great sloth-like creature, the 'megatherium', and the great armadillo, the 'glyptodon', and so on. and if you go to australia you find the same law holds good, namely, that that condition of organic nature which has preceded the one which now exists, presents differences perhaps of species, and of genera, but that the great types of organic structure are the same as those which now flourish. what meaning has this fact upon any other hypothesis or supposition than one of successive modification? but if the population of the world, in any age, is the result of the gradual modification of the forms which peopled it in the preceding age,--if that has been the case, it is intelligible enough; because we may expect that the creature that results from the modification of an elephantine mammal shall be something like an elephant, and the creature which is produced by the modification of an armadillo-like mammal shall be like an armadillo. upon that supposition, i say, the facts are intelligible; upon any other, that i am aware of, they are not. so far, the facts of palaeontology are consistent with almost any form of the doctrine of progressive modification; they would not be absolutely inconsistent with the wild speculations of de maillet, or with the less objectionable hypothesis of lamarck. but mr. darwin's views have one peculiar merit; and that is, that they are perfectly consistent with an array of facts which are utterly inconsistent with and fatal to, any other hypothesis of progressive modification which has yet been advanced. it is one remarkable peculiarity of mr. darwin's hypothesis that it involves no necessary progression or incessant modification, and that it is perfectly consistent with the persistence for any length of time of a given primitive stock, contemporaneously with its modifications. to return to the case of the domestic breeds of pigeons, for example; you have the dove-cot pigeon, which closely resembles the rock pigeon, from which they all started, existing at the same time with the others. and if species are developed in the same way in nature, a primitive stock and its modifications may, occasionally, all find the conditions fitted for their existence; and though they come into competition, to a certain extent, with one another, the derivative species may not necessarily extirpate the primitive one, or 'vice versa'. now palaeontology shows us many facts which are perfectly harmonious with these observed effects of the process by which mr. darwin supposes species to have originated, but which appear to me to be totally inconsistent with any other hypothesis which has been proposed. there are some groups of animals and plants, in the fossil world, which have been said to belong to "persistent types," because they have persisted, with very little change indeed, through a very great range of time, while everything about them has changed largely. there are families of fishes whose type of construction has persisted all the way from the carboniferous rock right up to the cretaceous; and others which have lasted through almost the whole range of the secondary rocks, and from the lias to the older tertiaries. it is something stupendous this--to consider a genus lasting without essential modifications through all this enormous lapse of time while almost everything else was changed and modified. thus i have no doubt that mr. darwin's hypothesis will be found competent to explain the majority of the phenomena exhibited by species in nature; but in an earlier lecture i spoke cautiously with respect to its power of explaining all the physiological peculiarities of species. there is, in fact, one set of these peculiarities which the theory of selective modification, as it stands at present, is not wholly competent to explain, and that is the group of phenomena which i mentioned to you under the name of hybridism, and which i explained to consist in the sterility of the offspring of certain species when crossed one with another. it matters not one whit whether this sterility is universal, or whether it exists only in a single case. every hypothesis is bound to explain, or, at any rate, not be inconsistent with, the whole of the facts which it professes to account for; and if there is a single one of these facts which can be shown to be inconsistent with (i do not merely mean inexplicable by, but contrary to) the hypothesis, the hypothesis falls to the ground,--it is worth nothing. one fact with which it is positively inconsistent is worth as much, and as powerful in negativing the hypothesis, as five hundred. if i am right in thus defining the obligations of an hypothesis, mr. darwin, in order to place his views beyond the reach of all possible assault, ought to be able to demonstrate the possibility of developing from a particular stock by selective breeding, two forms, which should either be unable to cross one with another, or whose cross-bred offspring should be infertile with one another. for, you see, if you have not done that you have not strictly fulfilled all the conditions of the problem; you have not shown that you can produce, by the cause assumed, all the phenomena which you have in nature. here are the phenomena of hybridism staring you in the face, and you cannot say, 'i can, by selective modification, produce these same results.' now, it is admitted on all hands that, at present, so far as experiments have gone, it has not been found possible to produce this complete physiological divergence by selective breeding. i stated this very clearly before, and i now refer to the point, because, if it could be proved, not only that this 'has' not been done, but that it 'cannot' be done; if it could be demonstrated that it is impossible to breed selectively, from any stock, a form which shall not breed with another, produced from the same stock; and if we were shown that this must be the necessary and inevitable results of all experiments, i hold that mr. darwin's hypothesis would be utterly shattered. but has this been done? or what is really the state of the case? it is simply that, so far as we have gone yet with our breeding, we have not produced from a common stock two breeds which are not more or less fertile with one another. i do not know that there is a single fact which would justify any one in saying that any degree of sterility has been observed between breeds absolutely known to have been produced by selective breeding from a common stock. on the other hand, i do not know that there is a single fact which can justify any one in asserting that such sterility cannot be produced by proper experimentation. for my own part, i see every reason to believe that it may, and will be so produced. for, as mr. darwin has very properly urged, when we consider the phenomena of sterility, we find they are most capricious; we do not know what it is that the sterility depends on. there are some animals which will not breed in captivity; whether it arises from the simple fact of their being shut up and deprived of their liberty, or not, we do not know, but they certainly will not breed. what an astounding thing this is, to find one of the most important of all functions annihilated by mere imprisonment! so, again, there are cases known of animals which have been thought by naturalists to be undoubted species, which have yielded perfectly fertile hybrids; while there are other species which present what everybody believes to be varieties [1] which are more or less infertile with one another. there are other cases which are truly extraordinary; there is one, for example, which has been carefully examined,--of two kinds of sea-weed, of which the male element of the one, which we may call a, fertilizes the female element of the other, b; while the male element of b will not fertilize the female element of a; so that, while the former experiment seems to show us that they are 'varieties', the latter leads to the conviction that they are 'species'. when we see how capricious and uncertain this sterility is, how unknown the conditions on which it depends, i say that we have no right to affirm that those conditions will not be better understood by and by, and we have no ground for supposing that we may not be able to experiment so as to obtain that crucial result which i mentioned just now. so that though mr. darwin's hypothesis does not completely extricate us from this difficulty at present, we have not the least right to say it will not do so. there is a wide gulf between the thing you cannot explain and the thing that upsets you altogether. there is hardly any hypothesis in this world which has not some fact in connection with it which has not been explained, but that is a very different affair to a fact that entirely opposes your hypothesis; in this case all you can say is, that your hypothesis is in the same position as a good many others. now, as to the third test, that there are no other causes competent to explain the phenomena, i explained to you that one should be able to say of an hypothesis, that no other known causes than those supposed by it are competent to give rise to the phenomena. here, i think, mr. darwin's view is pretty strong. i really believe that the alternative is either darwinism or nothing, for i do not know of any rational conception or theory of the organic universe which has any scientific position at all beside mr. darwin's. i do not know of any proposition that has been put before us with the intention of explaining the phenomena of organic nature, which has in its favour a thousandth part of the evidence which may be adduced in favour of mr. darwin's views. whatever may be the objections to his views, certainly all others are absolutely out of court. take the lamarckian hypothesis, for example. lamarck was a great naturalist, and to a certain extent went the right way to work; he argued from what was undoubtedly a true cause of some of the phenomena of organic nature. he said it is a matter of experience that an animal may be modified more or less in consequence of its desires and consequent actions. thus, if a man exercise himself as a blacksmith, his arms will become strong and muscular; such organic modification is a result of this particular action and exercise. lamarck thought that by a very simple supposition based on this truth he could explain the origin of the various animal species: he said, for example, that the short-legged birds which live on fish had been converted into the long-legged waders by desiring to get the fish without wetting their bodies, and so stretching their legs more and more through successive generations. if lamarck could have shown experimentally, that even races of animals could be produced in this way, there might have been some ground for his speculations. but he could show nothing of the kind, and his hypothesis has pretty well dropped into oblivion, as it deserved to do. i said in an earlier lecture that there are hypotheses and hypotheses, and when people tell you that mr. darwin's strongly-based hypothesis is nothing but a mere modification of lamarck's, you will know what to think of their capacity for forming a judgment on this subject. but you must recollect that when i say i think it is either mr. darwin's hypothesis or nothing; that either we must take his view, or look upon the whole of organic nature as an enigma, the meaning of which is wholly hidden from us; you must understand that i mean that i accept it provisionally, in exactly the same way as i accept any other hypothesis. men of science do not pledge themselves to creeds; they are bound by articles of no sort; there is not a single belief that it is not a bounden duty with them to hold with a light hand and to part with it cheerfully, the moment it is really proved to be contrary to any fact, great or small. and if, in course of time i see good reasons for such a proceeding, i shall have no hesitation in coming before you, and pointing out any change in my opinion without finding the slightest occasion to blush for so doing. so i say that we accept this view as we accept any other, so long as it will help us, and we feel bound to retain it only so long as it will serve our great purpose--the improvement of man's estate and the widening of his knowledge. the moment this, or any other conception, ceases to be useful for these purposes, away with it to the four winds; we care not what becomes of it! but to say truth, although it has been my business to attend closely to the controversies roused by the publication of mr. darwin's book, i think that not one of the enormous mass of objections and obstacles which have been raised is of any very great value, except that sterility case which i brought before you just now. all the rest are misunderstandings of some sort, arising either from prejudice, or want of knowledge, or still more from want of patience and care in reading the work. for you must recollect that it is not a book to be read with as much ease as its pleasant style may lead you to imagine. you spin through it as if it were a novel the first time you read it, and think you know all about it; the second time you read it you think you know rather less about it; and the third time, you are amazed to find how little you have really apprehended its vast scope and objects. i can positively say that i never take it up without finding in it some new view, or light, or suggestion that i have not noticed before. that is the best characteristic of a thorough and profound book; and i believe this feature of the 'origin of species' explains why so many persons have ventured to pass judgment and criticisms upon it which are by no means worth the paper they are written on. before concluding these lectures there is one point to which i must advert,--though, as mr. darwin has said nothing about man in his book, it concerns myself rather than him;--for i have strongly maintained on sundry occasions that if mr. darwin's views are sound, they apply as much to man as to the lower mammals, seeing that it is perfectly demonstrable that the structural differences which separate man from the apes are not greater than those which separate some apes from others. there cannot be the slightest doubt in the world that the argument which applies to the improvement of the horse from an earlier stock, or of ape from ape, applies to the improvement of man from some simpler and lower stock than man. there is not a single faculty--functional or structural, moral, intellectual, or instinctive,--there is no faculty whatever that is not capable of improvement; there is no faculty whatsoever which does not depend upon structure, and as structure tends to vary, it is capable of being improved. well, i have taken a good deal of pains at various times to prove this, and i have endeavoured to meet the objections of those who maintain, that the structural differences between man and the lower animals are of so vast a character and enormous extent, that even if mr. darwin's views are correct, you cannot imagine this particular modification to take place. it is, in fact, easy matter to prove that, so far as structure is concerned, man differs to no greater extent from the animals which are immediately below him than these do from other members of the same order. upon the other hand, there is no one who estimates more highly than i do the dignity of human nature, and the width of the gulf in intellectual and moral matters, which lies between man and the whole of the lower creation. but i find this very argument brought forward vehemently by some. "you say that man has proceeded from a modification of some lower animal, and you take pains to prove that the structural differences which are said to exist in his brain do not exist at all, and you teach that all functions, intellectual, moral, and others, are the expression or the result, in the long run, of structures, and of the molecular forces which they exert." it is quite true that i do so. "well, but," i am told at once, somewhat triumphantly, "you say in the same breath that there is a great moral and intellectual chasm between man and the lower animals. how is this possible when you declare that moral and intellectual characteristics depend on structure, and yet tell us that there is no such gulf between the structure of man and that of the lower animals?" i think that objection is based upon a misconception of the real relations which exist between structure and function, between mechanism and work. function is the expression of molecular forces and arrangements no doubt; but, does it follow from this, that variation in function so depends upon variation in structure that the former is always exactly proportioned to the latter? if there is no such relation, if the variation in function which follows on a variation in structure, may be enormously greater than the variation of the structure, then, you see, the objection falls to the ground. take a couple of watches--made by the same maker, and as completely alike as possible; set them upon the table, and the function of each--which is its rate of going--will be performed in the same manner, and you shall be able to distinguish no difference between them; but let me take a pair of pincers, and if my hand is steady enough to do it, let me just lightly crush together the bearings of the balance-wheel, or force to a slightly different angle the teeth of the escapement of one of them, and of course you know the immediate result will be that the watch, so treated, from that moment will cease to go. but what proportion is there between the structural alteration and the functional result? is it not perfectly obvious that the alteration is of the minutest kind, yet that slight as it is, it has produced an infinite difference in the performance of the functions of these two instruments? well, now, apply that to the present question. what is it that constitutes and makes man what he is? what is it but his power of language--that language giving him the means of recording his experience--making every generation somewhat wiser than its predecessor,--more in accordance with the established order of the universe? what is it but this power of speech, of recording experience, which enables men to be men--looking before and after and, in some dim sense, understanding the working of this wondrous universe--and which distinguishes man from the whole of the brute world? i say that this functional difference is vast, unfathomable, and truly infinite in its consequences; and i say at the same time, that it may depend upon structural differences which shall be absolutely inappreciable to us with our present means of investigation. what is this very speech that we are talking about? i am speaking to you at this moment, but if you were to alter, in the minutest degree, the proportion of the nervous forces now active in the two nerves which supply the muscles of my glottis, i should become suddenly dumb. the voice is produced only so long as the vocal chords are parallel; and these are parallel only so long as certain muscles contract with exact equality; and that again depends on the equality of action of those two nerves i spoke of. so that a change of the minutest kind in the structure of one of these nerves, or in the structure of the part in which it originates, or of the supply of blood to that part, or of one of the muscles to which it is distributed, might render all of us dumb. but a race of dumb men, deprived of all communication with those who could speak, would be little indeed removed from the brutes. and the moral and intellectual difference between them and ourselves would be practically infinite, though the naturalist should not be able to find a single shadow of even specific structural difference. but let me dismiss this question now, and, in conclusion, let me say that you may go away with it as my mature conviction, that mr. darwin's work is the greatest contribution which has been made to biological science since the publication of the 'regne animal' of cuvier, and since that of the 'history of development' of von baer. i believe that if you strip it of its theoretical part it still remains one of the greatest encyclopaedias of biological doctrine that any one man ever brought forth; and i believe that, if you take it as the embodiment of an hypothesis, it is destined to be the guide of biological and psychological speculation for the next three or four generations. [footnote 1: and as i conceive with very good reason; but if any objector urges that we cannot prove that they have been produced by artificial or natural selection, the objection must be admitted-ultrasceptical as it is. but in science, scepticism is a duty.] the perpetuation of living beings, hereditary transmission and variation by thomas henry huxley the inquiry which we undertook, at our last meeting, into the state of our knowledge of the causes of the phenomena of organic nature,--of the past and of the present,--resolved itself into two subsidiary inquiries: the first was, whether we know anything, either historically or experimentally, of the mode of origin of living beings; the second subsidiary inquiry was, whether, granting the origin, we know anything about the perpetuation and modifications of the forms of organic beings. the reply which i had to give to the first question was altogether negative, and the chief result of my last lecture was, that, neither historically nor experimentally, do we at present know anything whatsoever about the origin of living forms. we saw that, historically, we are not likely to know anything about it, although we may perhaps learn something experimentally; but that at present we are an enormous distance from the goal i indicated. i now, then, take up the next question, what do we know of the reproduction, the perpetuation, and the modifications of the forms of living beings, supposing that we have put the question as to their origination on one side, and have assumed that at present the causes of their origination are beyond us, and that we know nothing about them? upon this question the state of our knowledge is extremely different; it is exceedingly large, and, if not complete, our experience is certainly most extensive. it would be impossible to lay it all before you, and the most i can do, or need do to-night, is to take up the principal points and put them before you with such prominence as may subserve the purposes of our present argument. the method of the perpetuation of organic beings is of two kinds,--the asexual and the sexual. in the first the perpetuation takes place from and by a particular act of an individual organism, which sometimes may not be classed as belonging to any sex at all. in the second case, it is in consequence of the mutual action and interaction of certain portions of the organisms of usually two distinct individuals,--the male and the female. the cases of asexual perpetuation are by no means so common as the cases of sexual perpetuation; and they are by no means so common in the animal as in the vegetable world. you are all probably familiar with the fact, as a matter of experience, that you can propagate plants by means of what are called "cuttings;" for example, that by taking a cutting from a geranium plant, and rearing it properly, by supplying it with light and warmth and nourishment from the earth, it grows up and takes the form of its parent, having all the properties and peculiarities of the original plant. sometimes this process, which the gardener performs artificially, takes place naturally; that is to say, a little bulb, or portion of the plant, detaches itself, drops off, and becomes capable of growing as a separate thing. that is the case with many bulbous plants, which throw off in this way secondary bulbs, which are lodged in the ground and become developed into plants. this is an asexual process, and from it results the repetition or reproduction of the form of the original being from which the bulb proceeds. among animals the same thing takes place. among the lower forms of animal life, the infusorial animalculae we have already spoken of throw off certain portions, or break themselves up in various directions, sometimes transversely or sometimes longitudinally; or they may give off buds, which detach themselves and develop into their proper forms. there is the common fresh-water polype, for instance, which multiplies itself in this way. just in the same way as the gardener is able to multiply and reproduce the peculiarities and characters of particular plants by means of cuttings, so can the physiological experimentalist--as was shown by the abbe trembley many years ago--so can he do the same thing with many of the lower forms of animal life. m. de trembley showed that you could take a polype and cut it into two, or four, or many pieces, mutilating it in all directions, and the pieces would still grow up and reproduce completely the original form of the animal. these are all cases of asexual multiplication, and there are other instances, and still more extraordinary ones, in which this process takes place naturally, in a more hidden, a more recondite kind of way. you are all of you familiar with those little green insects, the 'aphis' or blight, as it is called. these little animals, during a very considerable part of their existence, multiply themselves by means of a kind of internal budding, the buds being developed into essentially asexual animals, which are neither male nor female; they become converted into young 'aphides', which repeat the process, and their offspring after them, and so on again; you may go on for nine or ten, or even twenty or more successions; and there is no very good reason to say how soon it might terminate, or how long it might not go on if the proper conditions of warmth and nourishment were kept up. sexual reproduction is quite a distinct matter. here, in all these cases, what is required is the detachment of two portions of the parental organisms, which portions we know as the egg and the spermatozoon. in plants it is the ovule and the pollen-grain, as in the flowering plants, or the ovule and the antherozooid, as in the flowerless. among all forms of animal life, the spermatozoa proceed from the male sex, and the egg is the product of the female. now, what is remarkable about this mode of reproduction is this, that the egg by itself, or the spermatozoa by themselves, are unable to assume the parental form; but if they be brought into contact with one another, the effect of the mixture of organic substances proceeding from two sources appears to confer an altogether new vigour to the mixed product. this process is brought about, as we all know, by the sexual intercourse of the two sexes, and is called the act of impregnation. the result of this act on the part of the male and female is, that the formation of a new being is set up in the ovule or egg; this ovule or egg soon begins to be divided and subdivided, and to be fashioned into various complex organisms, and eventually to develop into the form of one of its parents, as i explained in the first lecture. these are the processes by which the perpetuation of organic beings is secured. why there should be the two modes--why this re-invigoration should be required on the part of the female element we do not know; but it is most assuredly the fact, and it is presumable, that, however long the process of asexual multiplication could be continued, i say there is good reason to believe that it would come to an end if a new commencement were not obtained by a conjunction of the two sexual elements. that character which is common to these two distinct processes is this, that, whether we consider the reproduction, or perpetuation, or modification of organic beings as they take place asexually, or as they may take place sexually,--in either case, i say, the offspring has a constant tendency to assume, speaking generally, the character of the parent. as i said just now, if you take a slip of a plant, and tend it with care, it will eventually grow up and develop into a plant like that from which it had sprung; and this tendency is so strong that, as gardeners know, this mode of multiplying by means of cuttings is the only secure mode of propagating very many varieties of plants; the peculiarity of the primitive stock seems to be better preserved if you propagate it by means of a slip than if you resort to the sexual mode. again, in experiments upon the lower animals, such as the polype, to which i have referred, it is most extraordinary that, although cut up into various pieces, each particular piece will grow up into the form of the primitive stock; the head, if separated, will reproduce the body and the tail; and if you cut off the tail, you will find that that will reproduce the body and all the rest of the members, without in any way deviating from the plan of the organism from which these portions have been detached. and so far does this go, that some experimentalists have carefully examined the lower orders of animals,--among them the abbe spallanzani, who made a number of experiments upon snails and salamanders,--and have found that they might mutilate them to an incredible extent; that you might cut off the jaw or the greater part of the head, or the leg or the tail, and repeat the experiment several times, perhaps, cutting off the same member again and again; and yet each of those types would be reproduced according to the primitive type: nature making no mistake, never putting on a fresh kind of leg, or head, or tail, but always tending to repeat and to return to the primitive type. it is the same in sexual reproduction: it is a matter of perfectly common experience, that the tendency on the part of the offspring always is, speaking broadly, to reproduce the form of the parents. the proverb has it that the thistle does not bring forth grapes; so, among ourselves, there is always a likeness, more or less marked and distinct, between children and their parents. that is a matter of familiar and ordinary observation. we notice the same thing occurring in the cases of the domestic animals--dogs, for instance, and their offspring. in all these cases of propagation and perpetuation, there seems to be a tendency in the offspring to take the characters of the parental organisms. to that tendency a special name is given--it is called 'atavism', it expresses this tendency to revert to the ancestral type, and comes from the latin word 'atavus', ancestor. well, this 'atavism' which i shall speak of, is, as i said before, one of the most marked and striking tendencies of organic beings; but, side by side with this hereditary tendency there is an equally distinct and remarkable tendency to variation. the tendency to reproduce the original stock has, as it were, its limits, and side by side with it there is a tendency to vary in certain directions, as if there were two opposing powers working upon the organic being, one tending to take it in a straight line, and the other tending to make it diverge from that straight line, first to one side and then to the other. so that you see these two tendencies need not precisely contradict one another, as the ultimate result may not always be very remote from what would have been the case if the line had been quite straight. this tendency to variation is less marked in that mode of propagation which takes place asexually; it is in that mode that the minor characters of animal and vegetable structures are most completely preserved. still, it will happen sometimes, that the gardener, when he has planted a cutting of some favourite plant, will find, contrary to his expectation, that the slip grows up a little different from the primitive stock--that it produces flowers of a different colour or make, or some deviation in one way or another. this is what is called the 'sporting' of plants. in animals the phenomena of asexual propagation are so obscure, that at present we cannot be said to know much about them; but if we turn to that mode of perpetuation which results from the sexual process, then we find variation a perfectly constant occurrence, to a certain extent; and, indeed, i think that a certain amount of variation from the primitive stock is the necessary result of the method of sexual propagation itself; for, inasmuch as the thing propagated proceeds from two organisms of different sexes and different makes and temperaments, and as the offspring is to be either of one sex or the other, it is quite clear that it cannot be an exact diagonal of the two, or it would be of no sex at all; it cannot be an exact intermediate form between that of each of its parents--it must deviate to one side or the other. you do not find that the male follows the precise type of the male parent, nor does the female always inherit the precise characteristics of the mother,--there is always a proportion of the female character in the male offspring, and of the male character in the female offspring. that must be quite plain to all of you who have looked at all attentively on your own children or those of your neighbours; you will have noticed how very often it may happen that the son shall exhibit the maternal type of character, or the daughter possess the characteristics of the father's family. there are all sorts of intermixtures and intermediate conditions between the two, where complexion, or beauty, or fifty other different peculiarities belonging to either side of the house, are reproduced in other members of the same family. indeed, it is sometimes to be remarked in this kind of variation, that the variety belongs, strictly speaking, to neither of the immediate parents; you will see a child in a family who is not like either its father or its mother; but some old person who knew its grandfather or grandmother, or, it may be, an uncle, or, perhaps, even a more distant relative, will see a great similarity between the child and one of these. in this way it constantly happens that the characteristic of some previous member of the family comes out and is reproduced and recognised in the most unexpected manner. but apart from that matter of general experience, there are some cases which put that curious mixture in a very clear light. you are aware that the offspring of the ass and the horse, or rather of the he-ass and the mare, is what is called a mule; and, on the other hand, the offspring of the stallion and the she-ass is what is called a 'hinny'. i never saw one myself; but they have been very carefully studied. now, the curious thing is this, that although you have the same elements in the experiment in each case, the offspring is entirely different in character, according as the male influence comes from the ass or the horse. where the ass is the male, as in the case of the mule, you find that the head is like that of the ass, that the ears are long, the tail is tufted at the end, the feet are small, and the voice is an unmistakable bray; these are all points of similarity to the ass; but, on the other hand, the barrel of the body and the cut of the neck are much more like those of the mare. then, if you look at the hinny,--the result of the union of the stallion and the she-ass, then you find it is the horse that has the predominance; that the head is more like that of the horse, the ears are shorter, the legs coarser, and the type is altogether altered; while the voice, instead of being a bray, is the ordinary neigh of the horse. here, you see, is a most curious thing: you take exactly the same elements, ass and horse, but you combine the sexes in a different manner, and the result is modified accordingly. you have in this case, however, a result which is not general and universal--there is usually an important preponderance, but not always on the same side. here, then, is one intelligible, and, perhaps, necessary cause of variation: the fact, that there are two sexes sharing in the production of the offspring, and that the share taken by each is different and variable, not only for each combination, but also for different members of the same family. secondly, there is a variation, to a certain extent--though, in all probability, the influence of this cause has been very much exaggerated--but there is no doubt that variation is produced, to a certain extent, by what are commonly known as external conditions,--such as temperature, food, warmth, and moisture. in the long run, every variation depends, in some sense, upon external conditions, seeing that everything has a cause of its own. i use the term "external conditions" now in the sense in which it is ordinarily employed: certain it is, that external conditions have a definite effect. you may take a plant which has single flowers, and by dealing with the soil, and nourishment, and so on, you may by-and-by convert single flowers into double flowers, and make thorns shoot out into branches. you may thicken or make various modifications in the shape of the fruit. in animals, too, you may produce analogous changes in this way, as in the case of that deep bronze colour which persons rarely lose after having passed any length of time in tropical countries. you may also alter the development of the muscles very much, by dint of training; all the world knows that exercise has a great effect in this way; we always expect to find the arm of a blacksmith hard and wiry, and possessing a large development of the brachial muscles. no doubt training, which is one of the forms of external conditions, converts what are originally only instructions, teachings, into habits, or, in other words, into organizations, to a great extent; but this second cause of variation cannot be considered to be by any means a large one. the third cause that i have to mention, however, is a very extensive one. it is one that, for want of a better name, has been called "spontaneous variation;" which means that when we do not know anything about the cause of phenomena, we call it spontaneous. in the orderly chain of causes and effects in this world, there are very few things of which it can be said with truth that they are spontaneous. certainly not in these physical matters,--in these there is nothing of the kind,--everything depends on previous conditions. but when we cannot trace the cause of phenomena, we call them spontaneous. of these variations, multitudinous as they are, but little is known with perfect accuracy. i will mention to you some two or three cases, because they are very remarkable in themselves, and also because i shall want to use them afterwards. reaumur, a famous french naturalist, a great many years ago, in an essay which he wrote upon the art of hatching chickens,--which was indeed a very curious essay,--had occasion to speak of variations and monstrosities. one very remarkable case had come under his notice of a variation in the form of a human member, in the person of a maltese, of the name of gratio kelleia, who was born with six fingers upon each hand, and the like number of toes to each of his feet. that was a case of spontaneous variation. nobody knows why he was born with that number of fingers and toes, and as we don't know, we call it a case of "spontaneous" variation. there is another remarkable case also. i select these, because they happen to have been observed and noted very carefully at the time. it frequently happens that a variation occurs, but the persons who notice it do not take any care in noting down the particulars, until at length, when inquiries come to be made, the exact circumstances are forgotten; and hence, multitudinous as may be such "spontaneous" variations, it is exceedingly difficult to get at the origin of them. the second case is one of which you may find the whole details in the "philosophical transactions" for the year 1813, in a paper communicated by colonel humphrey to the president of the royal society,--"on a new variety in the breed of sheep," giving an account of a very remarkable breed of sheep, which at one time was well known in the northern states of america, and which went by the name of the ancon or the otter breed of sheep. in the year 1791, there was a farmer of the name of seth wright in massachusetts, who had a flock of sheep, consisting of a ram and, i think, of some twelve or thirteen ewes. of this flock of ewes, one at the breeding-time bore a lamb which was very singularly formed; it had a very long body, very short legs, and those legs were bowed! i will tell you by-and-by how this singular variation in the breed of sheep came to be noted, and to have the prominence that it now has. for the present, i mention only these two cases; but the extent of variation in the breed of animals is perfectly obvious to any one who has studied natural history with ordinary attention, or to any person who compares animals with others of the same kind. it is strictly true that there are never any two specimens which are exactly alike; however similar, they will always differ in some certain particular. now let us go back to atavism,--to the hereditary tendency i spoke of. what will come of a variation when you breed from it, when atavism comes, if i may say so, to intersect variation? the two cases of which i have mentioned the history, give a most excellent illustration of what occurs. gratio kelleia, the maltese, married when he was twenty-two years of age, and, as i suppose there were no six-fingered ladies in malta, he married an ordinary five-fingered person. the result of that marriage was four children; the first, who was christened salvator, had six fingers and six toes, like his father; the second was george, who had five fingers and toes, but one of them was deformed, showing a tendency to variation; the third was andre; he had five fingers and five toes, quite perfect; the fourth was a girl, marie; she had five fingers and five toes, but her thumbs were deformed, showing a tendency toward the sixth. these children grew up, and when they came to adult years, they all married, and of course it happened that they all married five-fingered and five-toed persons. now let us see what were the results. salvator had four children; they were two boys, a girl, and another boy; the first two boys and the girl were six-fingered and six-toed like their grandfather; the fourth boy had only five fingers and five toes. george had only four children; there were two girls with six fingers and six toes; there was one girl with six fingers and five toes on the right side, and five fingers and five toes on the left side, so that she was half and half. the last, a boy, had five fingers and five toes. the third, andre, you will recollect, was perfectly well-formed, and he had many children whose hands and feet were all regularly developed. marie, the last, who, of course, married a man who had only five fingers, had four children; the first, a boy, was born with six toes, but the other three were normal. now observe what very extraordinary phenomena are presented here. you have an accidental variation arising from what you may call a monstrosity; you have that monstrosity tendency or variation diluted in the first instance by an admixture with a female of normal construction, and you would naturally expect that, in the results of such an union, the monstrosity, if repeated, would be in equal proportion with the normal type; that is to say, that the children would be half and half, some taking the peculiarity of the father, and the others being of the purely normal type of the mother; but you see we have a great preponderance of the abnormal type. well, this comes to be mixed once more with the pure, the normal type, and the abnormal is again produced in large proportion, notwithstanding the second dilution. now what would have happened if these abnormal types had intermarried with each other; that is to say, suppose the two boys of salvator had taken it into their heads to marry their first cousins, the two first girls of george, their uncle? you will remember that these are all of the abnormal type of their grandfather. the result would probably have been, that their offspring would have been in every case a further development of that abnormal type. you see it is only in the fourth, in the person of marie, that the tendency, when it appears but slightly in the second generation, is washed out in the third, while the progeny of andre, who escaped in the first instance, escape altogether. we have in this case a good example of nature's tendency to the perpetuation of a variation. here it is certainly a variation which carried with it no use or benefit; and yet you see the tendency to perpetuation may be so strong, that, notwithstanding a great admixture of pure blood, the variety continues itself up to the third generation, which is largely marked with it. in this case, as i have said, there was no means of the second generation intermarrying with any but five-fingered persons, and the question naturally suggests itself, what would have been the result of such marriage? reaumur narrates this case only as far as the third generation. certainly it would have been an exceedingly curious thing if we could have traced this matter any further; had the cousins intermarried, a six-fingered variety of the human race might have been set up. to show you that this supposition is by no means an unreasonable one, let me now point out what took place in the case of seth wright's sheep, where it happened to be a matter of moment to him to obtain a breed or raise a flock of sheep like that accidental variety that i have described--and i will tell you why. in that part of massachusetts where seth wright was living, the fields were separated by fences, and the sheep, which were very active and robust, would roam abroad, and without much difficulty jump over these fences into other people's farms. as a matter of course, this exuberant activity on the part of the sheep constantly gave rise to all sorts of quarrels, bickerings, and contentions among the farmers of the neighbourhood; so it occurred to seth wright, who was, like his successors, more or less 'cute, that if he could get a stock of sheep like those with the bandy legs, they would not be able to jump over the fences so readily, and he acted upon that idea. he killed his old ram, and as soon as the young one arrived at maturity, he bred altogether from it. the result was even more striking than in the human experiment which i mentioned just now. colonel humphreys testifies that it always happened that the offspring were either pure ancons or pure ordinary sheep; that in no case was there any mixing of the ancons with the others. in consequence of this, in the course of a very few years, the farmer was able to get a very considerable flock of this variety, and a large number of them were spread throughout massachusetts. most unfortunately, however--i suppose it was because they were so common--nobody took enough notice of them to preserve their skeletons; and although colonel humphreys states that he sent a skeleton to the president of the royal society at the same time that he forwarded his paper, i am afraid that the variety has entirely disappeared; for a short time after these sheep had become prevalent in that district, the merino sheep were introduced; and as their wool was much more valuable, and as they were a quiet race of sheep, and showed no tendency to trespass or jump over fences, the otter breed of sheep, the wool of which was inferior to that of the merino, was gradually allowed to die out. you see that these facts illustrate perfectly well what may be done if you take care to breed from stocks that are similar to each other. after having got a variation, if, by crossing a variation with the original stock, you multiply that variation, and then take care to keep that variation distinct from the original stock, and make them breed together,--then you may almost certainly produce a race whose tendency to continue the variation is exceedingly strong. this is what is called "selection"; and it is by exactly the same process as that by which seth wright bred his ancon sheep, that our breeds of cattle, dogs, and fowls, are obtained. there are some possibilities of exception, but still, speaking broadly, i may say that this is the way in which all our varied races of domestic animals have arisen; and you must understand that it is not one peculiarity or one characteristic alone in which animals may vary. there is not a single peculiarity or characteristic of any kind, bodily or mental, in which offspring may not vary to a certain extent from the parent and other animals. among ourselves this is well known. the simplest physical peculiarity is mostly reproduced. i know a case of a man whose wife has the lobe of one of her ears a little flattened. an ordinary observer might scarcely notice it, and yet every one of her children has an approximation to the same peculiarity to some extent. if you look at the other extreme, too, the gravest diseases, such as gout, scrofula, and consumption, may be handed down with just the same certainty and persistence as we noticed in the perpetuation of the bandy legs of the ancon sheep. however, these facts are best illustrated in animals, and the extent of the variation, as is well known, is very remarkable in dogs. for example, there are some dogs very much smaller than others; indeed, the variation is so enormous that probably the smallest dog would be about the size of the head of the largest; there are very great variations in the structural forms not only of the skeleton but also in the shape of the skull, and in the proportions of the face and the disposition of the teeth. the pointer, the retriever, bulldog, and the terrier, differ very greatly, and yet there is every reason to believe that every one of these races has arisen from the same source,--that all the most important races have arisen by this selective breeding from accidental variation. a still more striking case of what may be done by selective breeding, and it is a better case, because there is no chance of that partial infusion of error to which i alluded, has been studied very carefully by mr. darwin,--the case of the domestic pigeons. i dare say there may be some among you who may be pigeon 'fanciers', and i wish you to understand that in approaching the subject, i would speak with all humility and hesitation, as i regret to say that i am not a pigeon fancier. i know it is a great art and mystery, and a thing upon which a man must not speak lightly; but i shall endeavour, as far as my understanding goes, to give you a summary of the published and unpublished information which i have gained from mr. darwin. among the enormous variety,--i believe there are somewhere about a hundred and fifty kinds of pigeons,--there are four kinds which may be selected as representing the extremest divergences of one kind from another. their names are the carrier, the pouter, the fantail, and the tumbler. in the large diagrams they are each represented in their relative sizes to each other. this first one is the carrier; you will notice this large excrescence on its beak; it has a comparatively small head; there is a bare space round the eyes; it has a long neck, a very long beak, very strong legs, large feet, long wings, and so on. the second one is the pouter, a very large bird, with very long legs and beak. it is called the pouter because it is in the habit of causing its gullet to swell up by inflating it with air. i should tell you that all pigeons have a tendency to do this at times, but in the pouter it is carried to an enormous extent. the birds appear to be quite proud of their power of swelling and puffing themselves out in this way; and i think it is about as droll a sight as you can well see to look at a cage full of these pigeons puffing and blowing themselves out in this ridiculous manner. the third kind i mentioned--the fantail--is a small bird, with exceedingly small legs and a very small beak. it is most curiously distinguished by the size and extent of its tail, which, instead of containing twelve feathers, may have many more,--say thirty, or even more--i believe there are some with as many as forty-two. this bird has a curious habit of spreading out the feathers of its tail in such a way that they reach forward, and touch its head; and if this can be accomplished, i believe it is looked upon as a point of great beauty. but here is the last great variety,--the tumbler; and of that great variety, one of the principal kinds, and one most prized, is the specimen represented here--the short-faced tumbler. its beak is reduced to a mere nothing. just compare the beak of this one and that of the first one, the carrier--i believe the orthodox comparison of the head and beak of a thoroughly well-bred tumbler is to stick an oat into a cherry, and that will give you the proper relative proportions of the head and beak. the feet and legs are exceedingly small, and the bird appears to be quite a dwarf when placed side by side with this great carrier. these are differences enough in regard to their external appearance; but these differences are by no means the whole or even the most important of the differences which obtain between these birds. there is hardly a single point of their structure which has not become more or less altered; and to give you an idea of how extensive these alterations are, i have here some very good skeletons, for which i am indebted to my friend, mr. tegetmeier, a great authority in these matters; by means of which, if you examine them by-and-by, you will be able to see the enormous difference in their bony structures. i had the privilege, some time ago, of access to some important mss. of mr. darwin, who, i may tell you, has taken very great pains and spent much valuable time and attention on the investigation of these variations, and getting together all the facts that bear upon them. i obtained from these mss. the following summary of the differences between the domestic breeds of pigeons; that is to say, a notification of the various points in which their organization differs. in the first place, the back of the skull may differ a good deal, and the development of the bones of the face may vary a great deal; the back varies a good deal; the shape of the lower jaw varies; the tongue varies very greatly, not only in correlation to the length and size of the beak, but it seems also to have a kind of independent variation of its own. then the amount of naked skin round the eyes, and at the base of the beak, may vary enormously; so may the length of the eyelids, the shape of the nostrils, and the length of the neck. i have already noticed the habit of blowing out the gullet, so remarkable in the pouter, and comparatively so in the others. there are great differences, too, in the size of the female and the male, the shape of the body, the number and width of the processes of the ribs, the development of the ribs, and the size, shape, and development of the breastbone. we may notice, too,--and i mention the fact because it has been disputed by what is assumed to be high authority,--the variation in the number of the sacral vertebrae. the number of these varies from eleven to fourteen, and that without any diminution in the number of the vertebrae of the back or of the tail. then the number and position of the tail-feathers may vary enormously, and so may the number of the primary and secondary feathers of the wings. again, the length of the feet and of the beak,--although they have no relation to each other, yet appear to go together,--that is, you have a long beak wherever you have long feet. there are differences also in the periods of the acquirement of the perfect plumage,--the size and shape of the eggs,--the nature of flight, and the powers of flight,--so-called "homing" birds having enormous flying powers; [1] while, on the other hand, the little tumbler is so called because of its extraordinary faculty of turning head over heels in the air, instead of pursuing a direct course. and, lastly, the dispositions and voices of the birds may vary. thus the case of the pigeons shows you that there is hardly a single particular,--whether of instinct, or habit, or bony structure, or of plumage,--of either the internal economy or the external shape, in which some variation or change may not take place, which, by selective breeding, may become perpetuated, and form the foundation of, and give rise to, a new race. [footnote 1: the "carrier," i learn from mr. tegetmeier, does not 'carry'; a high-bred bird of this breed being but a poor flier. the birds which fly long distances, and come home,--"homing" birds,--and are consequently used as carriers, are not "carriers" in the fancy sense.] if you carry in your mind's eye these four varieties of pigeons, you will bear with you as good a notion as you can have, perhaps, of the enormous extent to which a deviation from a primitive type may be carried by means of this process of selective breeding. criticisms on "the origin of species" 'the natural history review', 1864 [1] by thomas h. huxley in the course of the present year several foreign commentaries upon mr. darwin's great work have made their appearance. those who have perused that remarkable chapter of the 'antiquity of man,' in which sir charles lyell draws a parallel between the development of species and that of languages, will be glad to hear that one of the most eminent philologers of germany, professor schleicher, has, independently, published a most instructive and philosophical pamphlet (an excellent notice of which is to be found in the 'reader', for february 27th of this year) supporting similar views with all the weight of his special knowledge and established authority as a linguist. professor haeckel, to whom schleicher addresses himself, previously took occasion, in his splendid monograph on the 'radiolaria' [2], to express his high appreciation of, and general concordance with, mr. darwin's views. but the most elaborate criticisms of the 'origin of species' which have appeared are two works of very widely different merit, the one by professor kolliker, the well-known anatomist and histologist of wurzburg; the other by m. flourens, perpetual secretary of the french academy of sciences. professor kolliker's critical essay 'upon the darwinian theory' is, like all that proceeds from the pen of that thoughtful and accomplished writer, worthy of the most careful consideration. it comprises a brief but clear sketch of darwin's views, followed by an enumeration of the leading difficulties in the way of their acceptance; difficulties which would appear to be insurmountable to professor kolliker, inasmuch as he proposes to replace mr. darwin's theory by one which he terms the 'theory of heterogeneous generation.' we shall proceed to consider first the destructive, and secondly, the constructive portion of the essay. we regret to find ourselves compelled to dissent very widely from many of professor kolliker's remarks; and from none more thoroughly than from those in which he seeks to define what we may term the philosophical position of darwinism. "darwin," says professor kolliker, "is, in the fullest sense of the word, a teleologist. he says quite distinctly (first edition, pp. 199, 200) that every particular in the structure of an animal has been created for its benefit, and he regards the whole series of animal forms only from this point of view." and again: "7. the teleological general conception adopted by darwin is a mistaken one. "varieties arise irrespectively of the notion of purpose, or of utility, according to general laws of nature, and may be either useful, or hurtful, or indifferent. "the assumption that an organism exists only on account of some definite end in view, and represents something more than the incorporation of a general idea, or law, implies a one-sided conception of the universe. assuredly, every organ has, and every organism fulfils, its end, but its purpose is not the condition of its existence. every organism is also sufficiently perfect for the purpose it serves, and in that, at least, it is useless to seek for a cause of its improvement." it is singular how differently one and the same book will impress different minds. that which struck the present writer most forcibly on his first perusal of the 'origin of species' was the conviction that teleology, as commonly understood, had received its deathblow at mr. darwin's hands. for the teleological argument runs thus: an organ or organism (a) is precisely fitted to perform a function or purpose (b); therefore it was specially constructed to perform that function. in paley's famous illustration, the adaptation of all the parts of the watch to the function, or purpose, of showing the time, is held to be evidence that the watch was specially contrived to that end; on the ground, that the only cause we know of, competent to produce such an effect as a watch which shall keep time, is a contriving intelligence adapting the means directly to that end. suppose, however, that any one had been able to show that the watch had not been made directly by any person, but that it was the result of the modification of another watch which kept time but poorly; and that this again had proceeded from a structure which could hardly be called a watch at all--seeing that it had no figures on the dial and the hands were rudimentary; and that going back and back in time we came at last to a revolving barrel as the earliest traceable rudiment of the whole fabric. and imagine that it had been possible to show that all these changes had resulted, first, from a tendency of the structure to vary indefinitely; and secondly, from something in the surrounding world which helped all variations in the direction of an accurate time-keeper, and checked all those in other directions; then it is obvious that the force of paley's argument would be gone. for it would be demonstrated that an apparatus thoroughly well adapted to a particular purpose might be the result of a method of trial and error worked by unintelligent agents, as well as of the direct application of the means appropriate to that end, by an intelligent agent. now it appears to us that what we have here, for illustration's sake, supposed to be done with the watch, is exactly what the establishment of darwin's theory will do for the organic world. for the notion that every organism has been created as it is and launched straight at a purpose, mr. darwin substitutes the conception of something which may fairly be termed a method of trial and error. organisms vary incessantly; of these variations the few meet with surrounding conditions which suit them and thrive; the many are unsuited and become extinguished. according to teleology, each organism is like a rifle bullet fired straight at a mark; according to darwin, organisms are like grapeshot of which one hits something and the rest fall wide. for the teleologist an organism exists because it was made for the conditions in which it is found; for the darwinian an organism exists because, out of many of its kind, it is the only one which has been able to persist in the conditions in which it is found. teleology implies that the organs of every organism are perfect and cannot be improved; the darwinian theory simply affirms that they work well enough to enable the organism to hold its own against such competitors as it has met with, but admits the possibility of indefinite improvement. but an example may bring into clearer light the profound opposition between the ordinary teleological, and the darwinian, conception. cats catch mice, small birds and the like, very well. teleology tells us that they do so because they were expressly constructed for so doing--that they are perfect mousing apparatuses, so perfect and so delicately adjusted that no one of their organs could be altered, without the change involving the alteration of all the rest. darwinism affirms on the contrary, that there was no express construction concerned in the matter; but that among the multitudinous variations of the feline stock, many of which died out from want of power to resist opposing influences, some, the cats, were better fitted to catch mice than others, whence they throve and persisted, in proportion to the advantage over their fellows thus offered to them. far from imagining that cats exist 'in order' to catch mice well, darwinism supposes that cats exist 'because' they catch mice well--mousing being not the end, but the condition, of their existence. and if the cat type has long persisted as we know it, the interpretation of the fact upon darwinian principles would be, not that the cats have remained invariable, but that such varieties as have incessantly occurred have been, on the whole, less fitted to get on in the world than the existing stock. if we apprehend the spirit of the 'origin of species' rightly, then, nothing can be more entirely and absolutely opposed to teleology, as it is commonly understood, than the darwinian theory. so far from being a "teleologist in the fullest sense of the word," we would deny that he is a teleologist in the ordinary sense at all; and we should say that, apart from his merits as a naturalist, he has rendered a most remarkable service to philosophical thought by enabling the student of nature to recognise, to their fullest extent, those adaptations to purpose which are so striking in the organic world, and which teleology has done good service in keeping before our minds, without being false to the fundamental principles of a scientific conception of the universe. the apparently diverging teachings of the teleologist and of the morphologist are reconciled by the darwinian hypothesis. but leaving our own impressions of the 'origin of species,' and turning to those passages especially cited by professor kolliker, we cannot admit that they bear the interpretation he puts upon them. darwin, if we read him rightly, does 'not' affirm that every detail in the structure of an animal has been created for its benefit. his words are (p. 199):-"the foregoing remarks lead me to say a few words on the protest lately made by some naturalists against the utilitarian doctrine that every detail of structure has been produced for the good of its possessor. they believe that very many structures have been created for beauty in the eyes of man, or for mere variety. this doctrine, if true, would be absolutely fatal to my theory--yet i fully admit that many structures are of no direct use to their possessor." and after sundry illustrations and qualifications, he concludes (p. 200):-"hence every detail of structure in every living creature (making some little allowance for the direct action of physical conditions) may be viewed either as having been of special use to some ancestral form, or as being now of special use to the descendants of this form--either directly, or indirectly, through the complex laws of growth." but it is one thing to say, darwinically, that every detail observed in an animal's structure is of use to it, or has been of use to its ancestors; and quite another to affirm, teleologically, that every detail of an animal's structure has been created for its benefit. on the former hypothesis, for example, the teeth of the foetal balaena have a meaning; on the latter, none. so far as we are aware, there is not a phrase in the 'origin of species', inconsistent with professor kolliker's position, that "varieties arise irrespectively of the notion of purpose, or of utility, according to general laws of nature, and may be either useful, or hurtful, or indifferent." on the contrary, mr. darwin writes (summary of chap. v.):-"our ignorance of the laws of variation is profound. not in one case out of a hundred can we pretend to assign any reason why this or that part varies more or less from the same part in the parents.... the external conditions of life, as climate and food, etc., seem to have induced some slight modifications. habit, in producing constitutional differences, and use, in strengthening, and disuse, in weakening and diminishing organs, seem to have been more potent in their effects." and finally, as if to prevent all possible misconception, mr. darwin concludes his chapter on variation with these pregnant words:-"whatever the cause may be of each slight difference in the offspring from their parents--and a cause for each must exist--it is the steady accumulation, through natural selection of such differences, when beneficial to the individual, that gives rise to all the more important modifications of structure which the innumerable beings on the face of the earth are enabled to struggle with each other, and the best adapted to survive." we have dwelt at length upon this subject, because of its great general importance, and because we believe that professor kolliker's criticisms on this head are based upon a misapprehension of mr. darwin's views--substantially they appear to us to coincide with his own. the other objections which professor kolliker enumerates and discusses are the following [3]:-"1. no transitional forms between existing species are known; and known varieties, whether selected or spontaneous, never go so far as to establish new species." to this professor kolliker appears to attach some weight. he makes the suggestion that the short-faced tumbler pigeon may be a pathological product. "2. no transitional forms of animals are met with among the organic remains of earlier epochs." upon this, professor kolliker remarks that the absence of transitional forms in the fossil world, though not necessarily fatal to darwin's views, weakens his case. "3. the struggle for existence does not take place." to this objection, urged by pelzeln, kolliker, very justly, attaches no weight. "4. a tendency of organisms to give rise to useful varieties, and a natural selection, do not exist. "the varieties which are found arise in consequence of manifold external influences, and it is not obvious why they all, or partially, should be particularly useful. each animal suffices for its own ends, is perfect of its kind, and needs no further development. should, however, a variety be useful and even maintain itself, there is no obvious reason why it should change any further. the whole conception of the imperfection of organisms and the necessity of their becoming perfected is plainly the weakest side of darwin's theory, and a 'pis aller' (nothbehelf) because darwin could think of no other principle by which to explain the metamorphoses which, as i also believe, have occurred." here again we must venture to dissent completely from professor kolliker's conception of mr. darwin's hypothesis. it appears to us to be one of the many peculiar merits of that hypothesis that it involves no belief in a necessary and continual progress of organisms. again, mr. darwin, if we read him aright, assumes no special tendency of organisms to give rise to useful varieties, and knows nothing of needs of development, or necessity of perfection. what he says is, in substance: all organisms vary. it is in the highest degree improbable that any given variety should have exactly the same relations to surrounding conditions as the parent stock. in that case it is either better fitted (when the variation may be called useful), or worse fitted, to cope with them. if better, it will tend to supplant the parent stock; if worse, it will tend to be extinguished by the parent stock. if (as is hardly conceivable) the new variety is so perfectly adapted to the conditions that no improvement upon it is possible,--it will persist, because, though it does not cease to vary, the varieties will be inferior to itself. if, as is more probable, the new variety is by no means perfectly adapted to its conditions, but only fairly well adapted to them, it will persist, so long as none of the varieties which it throws off are better adapted than itself. on the other hand, as soon as it varies in a useful way, i.e. when the variation is such as to adapt it more perfectly to its conditions, the fresh variety will tend to supplant the former. so far from a gradual progress towards perfection forming any necessary part of the darwinian creed, it appears to us that it is perfectly consistent with indefinite persistence in one estate, or with a gradual retrogression. suppose, for example, a return of the glacial epoch and a spread of polar climatal conditions over the whole globe. the operation of natural selection under these circumstances would tend, on the whole, to the weeding out of the higher organisms and the cherishing of the lower forms of life. cryptogamic vegetation would have the advantage over phanerogamic; hydrozoa over corals; crustacea over insecta, and amphipoda and isopoda over the higher crustacea; cetaceans and seals over the primates; the civilization of the esquimaux over that of the european. "5. pelzeln has also objected that if the later organisms have proceeded from the earlier, the whole developmental series, from the simplest to the highest, could not now exist; in such a case the simpler organisms must have disappeared." to this professor kolliker replies, with perfect justice, that the conclusion drawn by pelzeln does not really follow from darwin's premisses, and that, if we take the facts of palaeontology as they stand, they rather support than oppose darwin's theory. "6. great weight must be attached to the objection brought forward by huxley, otherwise a warm supporter of darwin's hypothesis, that we know of no varieties which are sterile with one another, as is the rule among sharply distinguished animal forms. "if darwin is right, it must be demonstrated that forms may be produced by selection, which, like the present sharply distinguished animal forms, are infertile, when coupled with one another, and this has not been done." the weight of this objection is obvious; but our ignorance of the conditions of fertility and sterility, the want of carefully conducted experiments extending over long series of years, and the strange anomalies presented by the results of the cross-fertilization of many plants, should all, as mr. darwin has urged, be taken into account in considering it. the seventh objection is that we have already discussed ('supra', p. 178). the eighth and last stands as follows:-"8. the developmental theory of darwin is not needed to enable us to understand the regular harmonious progress of the complete series of organic forms from the simpler to the more perfect. "the existence of general laws of nature explains this harmony, even if we assume that all beings have arisen separately and independent of one another. darwin forgets that inorganic nature, in which there can be no thought of genetic connexion of forms, exhibits the same regular plan, the same harmony, as the organic world; and that, to cite only one example, there is as much a natural system of minerals as of plants and animals." we do not feel quite sure that we seize professor kolliker's meaning here, but he appears to suggest that the observation of the general order and harmony which pervade inorganic nature, would lead us to anticipate a similar order and harmony in the organic world. and this is no doubt true, but it by no means follows that the particular order and harmony observed among them should be that which we see. surely the stripes of dun horses, and the teeth of the foetal 'balaena', are not explained by the "existence of general laws of nature." mr. darwin endeavours to explain the exact order of organic nature which exists; not the mere fact that there is some order. and with regard to the existence of a natural system of minerals; the obvious reply is that there may be a natural classification of any objects--of stones on a sea-beach, or of works of art; a natural classification being simply an assemblage of objects in groups, so as to express their most important and fundamental resemblances and differences. no doubt mr. darwin believes that those resemblances and differences upon which our natural systems or classifications of animals and plants are based, are resemblances and differences which have been produced genetically, but we can discover no reason for supposing that he denies the existence of natural classifications of other kinds. and, after all, is it quite so certain that a genetic relation may not underlie the classification of minerals? the inorganic world has not always been what we see it. it has certainly had its metamorphoses, and, very probably, a long "entwickelungsgeschichte" out of a nebular blastema. who knows how far that amount of likeness among sets of minerals, in virtue of which they are now grouped into families and orders, may not be the expression of the common conditions to which that particular patch of nebulous fog, which may have been constituted by their atoms, and of which they may be, in the strictest sense, the descendants, was subjected? it will be obvious from what has preceded, that we do not agree with professor kolliker in thinking the objections which he brings forward so weighty as to be fatal to darwin's view. but even if the case were otherwise, we should be unable to accept the "theory of heterogeneous generation" which is offered as a substitute. that theory is thus stated:-"the fundamental conception of this hypothesis is, that, under the influence of a general law of development, the germs of organisms produce others different from themselves. this might happen (1) by the fecundated ova passing, in the course of their development, under particular circumstances, into higher forms; (2) by the primitive and later organisms producing other organisms without fecundation, out of germs or eggs (parthenogenesis)." in favour of this hypothesis, professor kolliker adduces the well-known facts of agamogenesis, or "alternate generation"; the extreme dissimilarity of the males and females of many animals; and of the males, females, and neuters of those insects which live in colonies: and he defines its relations to the darwinian theory as follows:-"it is obvious that my hypothesis is apparently very similar to darwin's, inasmuch as i also consider that the various forms of animals have proceeded directly from one another. my hypothesis of the creation of organisms by heterogeneous generation, however, is distinguished very essentially from darwin's by the entire absence of the principle of useful variations and their natural selection: and my fundamental conception is this, that a great plan of development lies at the foundation of the origin of the whole organic world, impelling the simpler forms to more and more complex developments. how this law operates, what influences determine the development of the eggs and germs, and impel them to assume constantly new forms, i naturally cannot pretend to say; but i can at least adduce the great analogy of the alternation of generations. if a 'bipinnaria', a 'brachialaria', a 'pluteus', is competent to produce the echinoderm, which is so widely different from it; if a hydroid polype can produce the higher medusa; if the vermiform trematode 'nurse' can develop within itself the very unlike 'cercaria', it will not appear impossible that the egg, or ciliated embryo, of a sponge, for once, under special conditions, might become a hydroid polype, or the embryo of a medusa, an echinoderm." it is obvious, from these extracts, that professor kolliker's hypothesis is based upon the supposed existence of a close analogy between the phenomena of agamogenesis and the production of new species from pre-existing ones. but is the analogy a real one? we think that it is not, and, by the hypothesis, cannot be. for what are the phenomena of agamogenesis, stated generally? an impregnated egg develops into an asexual form, a; this gives rise, asexually, to a second form or forms, b, more or less different from a. b may multiply asexually again; in the simpler cases, however, it does not, but, acquiring sexual characters, produces impregnated eggs from whence a, once more, arises. no case of agamogenesis is known in which, 'when a differs widely from b', it is itself capable of sexual propagation. no case whatever is known in which the progeny of b, by sexual generation, is other than a reproduction of a. but if this be a true statement of the nature of the process of agamogenesis, how can it enable us to comprehend the production of new species from already existing ones? let us suppose hyaenas to have preceded dogs, and to have produced the latter in this way. then the hyena will represent a, and the dog, b. the first difficulty that presents itself is that the hyena must be asexual, or the process will be wholly without analogy in the world of agamogenesis. but passing over this difficulty, and supposing a male and female dog to be produced at the same time from the hyaena stock, the progeny of the pair, if the analogy of the simpler kinds of agamogenesis [4] is to be followed, should be a litter, not of puppies, but of young hyenas. for the agamogenetic series is always, as we have seen, a: b: a: b, etc.; whereas, for the production of a new species, the series must be a: b: b: b, etc. the production of new species, or genera, is the extreme permanent divergence from the primitive stock. all known agamogenetic processes, on the other hand, end in a complete return to the primitive stock. how then is the production of new species to be rendered intelligible by the analogy of agamogenesis? the other alternative put by professor kolliker--the passage of fecundated ova in the course of their development into higher forms--would, if it occurred, be merely an extreme case of variation in the darwinian sense, greater in degree than, but perfectly similar in kind to, that which occurred when the well-known ancon ram was developed from an ordinary ewe's ovum. indeed we have always thought that mr. darwin has unnecessarily hampered himself by adhering so strictly to his favourite "natura non facit saltum." we greatly suspect that she does make considerable jumps in the way of variation now and then, and that these saltations give rise to some of the gaps which appear to exist in the series of known forms. strongly and freely as we have ventured to disagree with professor kolliker, we have always done so with regret, and we trust without violating that respect which is due, not only to his scientific eminence and to the careful study which he has devoted to the subject, but to the perfect fairness of his argumentation, and the generous appreciation of the worth of mr. darwin's labours which he always displays. it would be satisfactory to be able to say as much for m. flourens. but the perpetual secretary of the french academy of sciences deals with mr. darwin as the first napoleon would have treated an "ideologue;" and while displaying a painful weakness of logic and shallowness of information, assumes a tone of authority, which always touches upon the ludicrous, and sometimes passes the limits of good breeding. for example (p. 56):-"m. darwin continue: 'aucune distinction absolue n'a ete et ne pout etre etablie entre les especes et les varietes.' je vous ai deja dit que vous vous trompiez; une distinction absolue separe les varietes d'avec les especes." "je vous ai deja dit; moi, m. le secretaire perpetuel de l'academie des sciences: et vous 'qui n'etes rien, pas meme academicien;' what do you mean by asserting the contrary?' being devoid of the blessings of an academy in england, we are unaccustomed to see our ablest men treated in this fashion, even by a "perpetual secretary." or again, considering that if there is any one quality of mr. darwin's work to which friends and foes have alike borne witness, it is his candour and fairness in admitting and discussing objections, what is to be thought of m. flourens' assertion, that "m. darwin ne cite que les auteurs qui partagent ses opinions." (p. 40.) once more (p. 65):-"enfin l'ouvrage de m. darwin a paru. on ne peut qu'etre frappe du talent de l'auteur. mais que d'idees obscures, que d'idees fausses! quel jargon metaphysique jete mal a propos dans l'histoire naturelle, qui tombe dans le galimatias des qu'elle sort des idees claires, des idees justes! quel langage pretentieux et vide! quelles personifications pueriles et surannees! o lucidite! o solidite de l'esprit francais, que devenez-vous?" "obscure ideas," "metaphysical jargon," "pretentious and empty language," "puerile and superannuated personifications." mr. darwin has many and hot opponents on this side of the channel and in germany, but we do not recollect to have found precisely these sins in the long catalogue of those hitherto laid to his charge. it is worth while, therefore, to examine into these discoveries effected solely by the aid of the "lucidity and solidity" of the mind of m. flourens. according to m. flourens, mr. darwin's great error is that he has personified nature (p. 10), and further that he has "imagined a natural selection: he imagines afterwards that this power of selection (pouvoir d'lire) which he gives to nature is similar to the power of man. these two suppositions admitted, nothing stops him: he plays with nature as he likes, and makes her do all he pleases." (p. 6.) and this is the way m. flourens extinguishes natural selection: "voyons donc encore une fois, ce qu'il peut y avoir de fonde dans ce qu'on nomme election naturelle. "l'election naturelle n'est sous un autre nom que la nature. pour un etre organise, la nature n'est que l'organisation, ni plus ni moins. "il faudra donc aussi personnifier l'organisation, et dire que l'organisation choisit l'organisation. l'election naturelle est cette forme substantielle dont on jouait autrefois avec tant de facilite. aristote disait que 'si l'art de batir etait dans le bois, cet art agirait comme la nature.' a la place de l'art de batir m. darwin met l'election naturelle, et c'est tout un: l'un n'est pas plus chimerique que l'autre." (p.31.) and this is really all that m. flourens can make of natural selection. we have given the original, in fear lest a translation should be regarded as a travesty; but with the original before the reader, we may try to analyse the passage. "for an organized being, nature is only organization, neither more nor less." organized beings then have absolutely no relation to inorganic nature: a plant does not, depend on soil or sunshine, climate, depth in the ocean, height above it; the quantity of saline matters in water have no influence upon animal life; the substitution of carbonic acid for oxygen in our atmosphere would hurt nobody! that these are absurdities no one should know better than m. flourens; but they are logical deductions from the assertion just quoted, and from the further statement that natural selection means only that "organization chooses and selects organization." for if it be once admitted (what no sane man denies) that the chances of life of any given organism are increased by certain conditions (a) and diminished by their opposites (b), then it is mathematically certain that any change of conditions in the direction of (a) will exercise a selective influence in favour of that organism, tending to its increase and multiplication, while any change in the direction of (b) will exercise a selective influence against that organism, tending to its decrease and extinction. or, on the other hand, conditions remaining the same, let a given organism vary (and no one doubts that they do vary) in two directions: into one form (a) better fitted to cope with these conditions than the original stock, and a second (b) less well adapted to them. then it is no less certain that the conditions in question must exercise a selective influence in favour of (a) and against ( b), so that (a) will tend to predominance, and (b) to extirpation. that m. flourens should be unable to perceive the logical necessity of these simple arguments, which lie at the foundation of all mr. darwin's reasoning; that he should confound an irrefragable deduction from the observed relations of organisms to the conditions which lie around them, with a metaphysical "forme substantielle," or a chimerical personification of the powers of nature, would be incredible, were it not that other passages of his work leave no room for doubt upon the subject. "on imagine une 'election naturelle' que, pour plus de menagement, on me dit etre inconsciente, sans s'apercevoir que le contre-sens litteral est precisement la: 'election inconsciente'." (p. 52.) "j'ai deja dit ce qu'il faut penser de 'l'election naturelle'. ou 'l'election naturelle' n'est rien, ou c'est la nature: mais la nature douee 'd'election', mais la nature personnifiee: derniere erreur du dernier siecle: le xixe fait plus de personnifications." (p. 53.) m. flourens cannot imagine an unconscious selection--it is for him a contradiction in terms. did m. flourens ever visit one of the prettiest watering-places of "la belle france," the baie d'arcachon? if so, he will probably have passed through the district of the landes, and will have had an opportunity of observing the formation of "dunes" on a grand scale. what are these "dunes"? the winds and waves of the bay of biscay have not much consciousness, and yet they have with great care "selected," from among an infinity of masses of silex of all shapes and sizes, which have been submitted to their action, all the grains of sand below a certain size, and have heaped them by themselves over a great area. this sand has been "unconsciously selected" from amidst the gravel in which it first lay with as much precision as if man had "consciously selected" it by the aid of a sieve. physical geology is full of such selections--of the picking out of the soft from the hard, of the soluble from the insoluble, of the fusible from the infusible, by natural agencies to which we are certainly not in the habit of ascribing consciousness. but that which wind and sea are to a sandy beach, the sum of influences, which we term the "conditions of existence," is to living organisms. the weak are sifted out from the strong. a frosty night "selects" the hardy plants in a plantation from among the tender ones as effectually as if it were the wind, and they, the sand and pebbles, of our illustration; or, on the other hand, as if the intelligence of a gardener had been operative in cutting the weaker organisms down. the thistle, which has spread over the pampas, to the destruction of native plants, has been more effectually "selected" by the unconscious operation of natural conditions than if a thousand agriculturists had spent their time in sowing it. it is one of mr. darwin's many great services to biological science that he has demonstrated the significance of these facts. he has shown that--given variation and given change of conditions--the inevitable result is the exercise of such an influence upon organisms that one is helped and another is impeded; one tends to predominate, another to disappear; and thus the living world bears within itself, and is surrounded by, impulses towards incessant change. but the truths just stated are as certain as any other physical laws, quite independently of the truth, or falsehood, of the hypothesis which mr. darwin has based upon them; and that m. flourens, missing the substance and grasping at a shadow, should be blind to the admirable exposition of them, which mr. darwin has given, and see nothing there but a "derniere erreur du dernier siecle "--a personification of nature--leads us indeed to cry with him: "o lucidite! o solidite de l'esprit francais, que devenez-vous?" m. flourens has, in fact, utterly failed to comprehend the first principles of the doctrine which he assails so rudely. his objections to details are of the old sort, so battered and hackneyed on this side of the channel, that not even a quarterly reviewer could be induced to pick them up for the purpose of pelting mr. darwin over again. we have cuvier and the mummies; m. roulin and the domesticated animals of america; the difficulties presented by hybridism and by palaeontology; darwinism a 'rifacciamento' of de maillet and lamarck; darwinism a system without a commencement, and its author bound to believe in m. pouchet, etc. etc. how one knows it all by heart, and with what relief one reads at p. 65-"je laisse m. darwin!" but we cannot leave m. flourens without calling our readers' attention to his wonderful tenth chapter, "de la preexistence des germes et de l'epigenese," which opens thus:-"spontaneous generation is only a chimaera. this point established, two hypotheses remain: that of 'pre-existence' and that of 'epigenesis'. the one of these hypotheses has as little foundation as the other." (p. 163.) "the doctrine of 'epigenesis' is derived from harvey: following by ocular inspection the development of the new being in the windsor does, he saw each part appear successively, and taking the moment of 'appearance' for the moment of 'formation' he imagined 'epigenesis'." (p. 165.) on the contrary, says m. flourens (p. 167), "the new being is formed at a stroke ('tout d'un coup') as a whole, instantaneously; it is not formed part by part, and at different times. it is formed at once at the single 'individual' moment at which the conjunction of the male and female elements takes place." it will be observed that m. flourens uses language which cannot be mistaken. for him, the labours of von baer, of rathke, of coste, and their contemporaries and successors in germany, france, and england, are non-existent: and, as darwin "imagina" natural selection, so harvey "imagina" that doctrine which gives him an even greater claim to the veneration of posterity than his better known discovery of the circulation of the blood. language such as that we have quoted is, in fact, so preposterous, so utterly incompatible with anything but absolute ignorance of some of the best established facts, that we should have passed it over in silence had it not appeared to afford some clue to m. flourens' unhesitating, 'a priori', repudiation of all forms of the doctrine of progressive modification of living beings. he whose mind remains uninfluenced by an acquaintance with the phenomena of development, must indeed lack one of the chief motives towards the endeavour to trace a genetic relation between the different existing forms of life. those who are ignorant of geology, find no difficulty in believing that the world was made as it is; and the shepherd, untutored in history, sees no reason to regard the green mounds which indicate the site of a roman camp, as aught but part and parcel of the primeval hill-side. so m. flourens, who believes that embryos are formed "tout d'un coup," naturally finds no difficulty in conceiving that species came into existence in the same way. [footnote 1: the natural history review', 1864. 1. ueber die darwin'sche sch pfungstheorie; ein vortrag, von a. k lliker. leipzig, 1864. 2. examination du livre de m. darwin sur l'origine des especes. par p. flourens. paris, 1864.] [footnote 2: 'die radiolarien: eine monographie', p. 231.] [footnote 3: space will not allow us to give professor kolliker's arguments in detail; our readers will find a full and accurate version of them in the 'reader' for august 13th and 20th, 1864.] [footnote 4: if, on the contrary, we follow the analogy of the more complex forms of agamogenesis, such as that exhibited by some 'trematoda' and by the 'aphides', the hyaena must produce, asexually, a brood of asexual dogs, from which other sexless dogs must proceed. at the end of a certain number of terms of the series, the dogs would acquire sexes and generate young; but these young would be, not dogs, but hyaenas. in fact, we have 'demonstrated', in agamogenetic phenomena, that inevitable recurrence to the original type, which is 'asserted' to be true of variations in general, by mr. darwin's opponents; and which, if the assertion could be changed into a demonstration would, in fact, be fatal to his hypothesis.] the past condition of organic nature lecture ii. (of vi.), lectures to working men, at the museum of practical geology, 1863, on darwin's work: "origin of species". by thomas h. huxley in the lecture which i delivered last monday evening, i endeavoured to sketch in a very brief manner, but as well as the time at my disposal would permit, the present condition of organic nature, meaning by that large title simply an indication of the great, broad, and general principles which are to be discovered by those who look attentively at the phenomena of organic nature as at present displayed. the general result of our investigations might be summed up thus: we found that the multiplicity of the forms of animal life, great as that may be, may be reduced to a comparatively few primitive plans or types of construction; that a further study of the development of those different forms revealed to us that they were again reducible, until we at last brought the infinite diversity of animal, and even vegetable life, down to the primordial form of a single cell. we found that our analysis of the organic world, whether animals or plants, showed, in the long run, that they might both be reduced into, and were, in fact, composed of, the same constituents. and we saw that the plant obtained the materials constituting its substance by a peculiar combination of matters belonging entirely to the inorganic world; that, then, the animal was constantly appropriating the nitrogenous matters of the plant to its own nourishment, and returning them back to the inorganic world, in what we spoke of as its waste; and that finally, when the animal ceased to exist, the constituents of its body were dissolved and transmitted to that inorganic world whence they had been at first abstracted. thus we saw in both the blade of grass and the horse but the same elements differently combined and arranged. we discovered a continual circulation going on,--the plant drawing in the elements of inorganic nature and combining them into food for the animal creation; the animal borrowing from the plant the matter for its own support, giving off during its life products which returned immediately to the inorganic world; and that, eventually, the constituent materials of the whole structure of both animals and plants were thus returned to their original source: there was a constant passage from one state of existence to another, and a returning back again. lastly, when we endeavoured to form some notion of the nature of the forces exercised by living beings, we discovered that they--if not capable of being subjected to the same minute analysis as the constituents of those beings themselves--that they were correlative with--that they were the equivalents of the forces of inorganic nature--that they were, in the sense in which the term is now used, convertible with them. that was our general result. and now, leaving the present, i must endeavour in the same manner to put before you the facts that are to be discovered in the past history of the living world, in the past conditions of organic nature. we have, to-night, to deal with the facts of that history--a history involving periods of time before which our mere human records sink into utter insignificance--a history the variety and physical magnitude of whose events cannot even be foreshadowed by the history of human life and human phenomena--a history of the most varied and complex character. we must deal with the history, then, in the first place, as we should deal with all other histories. the historical student knows that his first business should be to inquire into the validity of his evidence, and the nature of the record in which the evidence is contained, that he may be able to form a proper estimate of the correctness of the conclusions which have been drawn from that evidence. so, here, we must pass, in the first place, to the consideration of a matter which may seem foreign to the question under discussion. we must dwell upon the nature of the records, and the credibility of the evidence they contain; we must look to the completeness or incompleteness of those records themselves, before we turn to that which they contain and reveal. the question of the credibility of the history, happily for us, will not require much consideration, for, in this history, unlike those of human origin, there can be no cavilling, no differences as to the reality and truth of the facts of which it is made up; the facts state themselves, and are laid out clearly before us. but, although one of the greatest difficulties of the historical student is cleared out of our path, there are other difficulties--difficulties in rightly interpreting the facts as they are presented to us--which may be compared with the greatest difficulties of any other kinds of historical study. what is this record of the past history of the globe, and what are the questions which are involved in an inquiry into its completeness or incompleteness? that record is composed of mud; and the question which we have to investigate this evening resolves itself into a question of the formation of mud. you may think, perhaps, that this is a vast step--of almost from the sublime to the ridiculous--from the contemplation of the history of the past ages of the world's existence to the consideration of the history of the formation of mud! but, in nature, there is nothing mean and unworthy of attention; there is nothing ridiculous or contemptible in any of her works; and this inquiry, you will soon see, i hope, takes us to the very root and foundations of our subject. how, then, is mud formed? always, with some trifling exception, which i need not consider now--always, as the result of the action of water, wearing down and disintegrating the surface of the earth and rocks with which it comes in contact--pounding and grinding it down, and carrying the particles away to places where they cease to be disturbed by this mechanical action, and where they can subside and rest. for the ocean, urged by winds, washes, as we know, a long extent of coast, and every wave, loaded as it is with particles of sand and gravel as it breaks upon the shore, does something towards the disintegrating process. and thus, slowly but surely, the hardest rocks are gradually ground down to a powdery substance; and the mud thus formed, coarser or finer, as the case may be, is carried by the rush of the tides, or currents, till it reaches the comparatively deeper parts of the ocean, in which it can sink to the bottom, that is, to parts where there is a depth of about fourteen or fifteen fathoms, a depth at which the water is, usually, nearly motionless, and in which, of course, the finer particles of this detritus, or mud as we call it, sinks to the bottom. or, again, if you take a river, rushing down from its mountain sources, brawling over the stones and rocks that intersect its path, loosening, removing, and carrying with it in its downward course the pebbles and lighter matters from its banks, it crushes and pounds down the rocks and earths in precisely the same way as the wearing action of the sea waves. the matters forming the deposit are torn from the mountain-side and whirled impetuously into the valley, more slowly over the plain, thence into the estuary, and from the estuary they are swept into the sea. the coarser and heavier fragments are obviously deposited first, that is, as soon as the current begins to lose its force by becoming amalgamated with the stiller depths of the ocean, but the finer and lighter particles are carried further on, and eventually deposited in a deeper and stiller portion of the ocean. it clearly follows from this that mud gives us a chronology; for it is evident that supposing this, which i now sketch, to be the sea bottom, and supposing this to be a coast-line; from the washing action of the sea upon the rock, wearing and grinding it down into a sediment of mud, the mud will be carried down, and at length, deposited in the deeper parts of this sea bottom, where it will form a layer; and then, while that first layer is hardening, other mud which is coming from the same source will, of course, be carried to the same place; and, as it is quite impossible for it to get beneath the layer already there, it deposits itself above it, and forms another layer, and in that way you gradually have layers of mud constantly forming and hardening one above the other, and conveying a record of time. it is a necessary result of the operation of the law of gravitation that the uppermost layer shall be the youngest and the lowest the oldest, and that the different beds shall be older at any particular point or spot in exactly the ratio of their depth from the surface. so that if they were upheaved afterwards, and you had a series of these different layers of mud, converted into sandstone, or limestone, as the case might be, you might be sure that the bottom layer was deposited first, and that the upper layers were formed afterwards. here, you see, is the first step in the history--these layers of mud give us an idea of time. the whole surface of the earth,--i speak broadly, and leave out minor qualifications,--is made up of such layers of mud, so hard, the majority of them, that we call them rock whether limestone or sandstone, or other varieties of rock. and, seeing that every part of the crust of the earth is made up in this way, you might think that the determination of the chronology, the fixing of the time which it has taken to form this crust is a comparatively simple matter. take a broad average, ascertain how fast the mud is deposited upon the bottom of the sea, or in the estuary of rivers; take it to be an inch, or two, or three inches a year, or whatever you may roughly estimate it at; then take the total thickness of the whole series of stratified rocks, which geologists estimate at twelve or thirteen miles, or about seventy thousand feet, make a sum in short division, divide the total thickness by that of the quantity deposited in one year, and the result will, of course, give you the number of years which the crust has taken to form. truly, that looks a very simple process! it would be so except for certain difficulties, the very first of which is that of finding how rapidly sediments are deposited; but the main difficulty--a difficulty which renders any certain calculations of such a matter out of the question--is this, the sea-bottom on which the deposit takes place is continually shifting. instead of the surface of the earth being that stable, fixed thing that it is popularly believed to be, being, in common parlance, the very emblem of fixity itself, it is incessantly moving, and is, in fact, as unstable as the surface of the sea, except that its undulations are infinitely slower and enormously higher and deeper. now, what is the effect of this oscillation? take the case to which i have previously referred. the finer or coarser sediments that are carried down by the current of the river, will only be carried out a certain distance, and eventually, as we have already seen, on reaching the stiller part of the ocean, will be deposited at the bottom. let c y (fig. 4) be the sea-bottom, y d the shore, x y the sea-level, then the coarser deposit will subside over the region b, the finer over a, while beyond a there will be no deposit at all; and, consequently, no record will be kept, simply because no deposit is going on. now, suppose that the whole land, c, d, which we have regarded as stationary, goes down, as it does so, both a and b go further out from the shore, which will be at y1; x1, y1, being the new sea-level. the consequence will be that the layer of mud (a), being now, for the most part, further than the force of the current is strong enough to convey even the finest 'debris', will, of course, receive no more deposits, and having attained a certain thickness will now grow no thicker. we should be misled in taking the thickness of that layer, whenever it may be exposed to our view, as a record of time in the manner in which we are now regarding this subject, as it would give us only an imperfect and partial record: it would seem to represent too short a period of time. [illustration: fig.4.] suppose, on the other hand, that the land (c d) had gone on rising slowly and gradually--say an inch or two inches in the course of a century,--what would be the practical effect of that movement? why, that the sediment a and b which has been already deposited, would eventually be brought nearer to the shore-level, and again subjected to the wear and tear of the sea; and directly the sea begins to act upon it, it would of course soon cut up and carry it away, to a greater or less extent, to be re-deposited further out. well, as there is, in all probability, not one single spot on the whole surface of the earth, which has not been up and down in this way a great many times, it follows that the thickness of the deposits formed at any particular spot cannot be taken (even supposing we had at first obtained correct data as to the rate at which they took place) as affording reliable information as to the period of time occupied in its deposit. so that you see it is absolutely necessary from these facts, seeing that our record entirely consists of accumulations of mud, superimposed one on the other; seeing in the next place that any particular spots on which accumulations have occurred, have been constantly moving up and down, and sometimes out of the reach of a deposit, and at other times its own deposit broken up and carried away, it follows that our record must be in the highest degree imperfect, and we have hardly a trace left of thick deposits, or any definite knowledge of the area that they occupied, in a great many cases. and mark this! that supposing even that the whole surface of the earth had been accessible to the geologist,--that man had had access to every part of the earth, and had made sections of the whole, and put them all together,--even then his record must of necessity be imperfect. but to how much has man really access? if you will look at this map you will see that it represents the proportion of the sea to the earth: this coloured part indicates all the dry land, and this other portion is the water. you will notice at once that the water covers three-fifths of the whole surface of the globe, and has covered it in the same manner ever since man has kept any record of his own observations, to say nothing of the minute period during which he has cultivated geological inquiry. so that three-fifths of the surface of the earth is shut out from us because it is under the sea. let us look at the other two-fifths, and see what are the countries in which anything that may be termed searching geological inquiry has been carried out: a good deal of france, germany, and great britain and ireland, bits of spain, of italy, and of russia, have been examined, but of the whole great mass of africa, except parts of the southern extremity, we know next to nothing; little bits of india, but of the greater part of the asiatic continent nothing; bits of the northern american states and of canada, but of the greater part of the continent of north america, and in still larger proportion, of south america, nothing! under these circumstances, it follows that even with reference to that kind of imperfect information which we can possess, it is only of about the ten-thousandth part of the accessible parts of the earth that has been examined properly. therefore, it is with justice that the most thoughtful of those who are concerned in these inquiries insist continually upon the imperfection of the geological record; for, i repeat, it is absolutely necessary, from the nature of things, that that record should be of the most fragmentary and imperfect character. unfortunately this circumstance has been constantly forgotten. men of science, like young colts in a fresh pasture, are apt to be exhilarated on being turned into a new field of inquiry, to go off at a hand-gallop, in total disregard of hedges and ditches, losing sight of the real limitation of their inquiries, and to forget the extreme imperfection of what is really known. geologists have imagined that they could tell us what was going on at all parts of the earth's surface during a given epoch; they have talked of this deposit being contemporaneous with that deposit, until, from our little local histories of the changes at limited spots of the earth's surface, they have constructed a universal history of the globe as full of wonders and portents as any other story of antiquity. but what does this attempt to construct a universal history of the globe imply? it implies that we shall not only have a precise knowledge of the events which have occurred at any particular point, but that we shall be able to say what events, at any one spot, took place at the same time with those at other spots. let us see how far that is in the nature of things practicable. suppose that here i make a section of the lake of killarney, and here the section of another lake--that of loch lomond in scotland for instance. the rivers that flow into them are constantly carrying down deposits of mud, and beds, or strata, are being as constantly formed, one above the other, at the bottom of those lakes. now, there is not a shadow of doubt that in these two lakes the lower beds are all older than the upper--there is no doubt about that; but what does 'this' tell us about the age of any given bed in loch lomond, as compared with that of any given bed in the lake of killarney? it is, indeed, obvious that if any two sets of deposits are separated and discontinuous, there is absolutely no means whatever given you by the nature of the deposit of saying whether one is much younger or older than the other; but you may say, as many have said and think, that the case is very much altered if the beds which we are comparing are continuous. suppose two beds of mud hardened into rock,--a and b-are seen in section. (fig. 5.) [illustration: fig. 5.] well, you say, it is admitted that the lowermost bed is always the older. very well; b, therefore, is older than a. no doubt, 'as a whole', it is so; or if any parts of the two beds which are in the same vertical line are compared, it is so. but suppose you take what seems a very natural step further, and say that the part 'a' of the bed a is younger than the part 'b' of the bed b. is this sound reasoning? if you find any record of changes taking place at 'b', did they occur before any events which took place while 'a' was being deposited? it looks all very plain sailing, indeed, to say that they did; and yet there is no proof of anything of the kind. as the former director of this institution, sir h. de la beche, long ago showed, this reasoning may involve an entire fallacy. it is extremely possible that 'a' may have been deposited ages before 'b'. it is very easy to understand how that can be. to return to fig. 4; when a and b were deposited, they were 'substantially' contemporaneous; a being simply the finer deposit, and b the coarser of the same detritus or waste of land. now suppose that that sea-bottom goes down (as shown in fig. 4), so that the first deposit is carried no farther than 'a', forming the bed al, and the coarse no farther than 'b', forming the bed b1, the result will be the formation of two continuous beds, one of fine sediment (a a1) over-lapping another of coarse sediment (b b1). now suppose the whole sea-bottom is raised up, and a section exposed about the point al; no doubt, 'at this spot', the upper bed is younger than the lower. but we should obviously greatly err if we concluded that the mass of the upper bed at a was younger than the lower bed at b; for we have just seen that they are contemporaneous deposits. still more should we be in error if we supposed the upper bed at a to be younger than the continuation of the lower bed at bl; for a was deposited long before b1. in fine, if, instead of comparing immediately adjacent parts of two beds, one of which lies upon another, we compare distant parts, it is quite possible that the upper may be any number of years older than the under, and the under any number of years younger than the upper. now you must not suppose that i put this before you for the purpose of raising a paradoxical difficulty; the fact is, that the great mass of deposits have taken place in sea-bottoms which are gradually sinking, and have been formed under the very conditions i am here supposing. do not run away with the notion that this subverts the principle i laid down at first. the error lies in extending a principle which is perfectly applicable to deposits in the same vertical line to deposits which are not in that relation to one another. it is in consequence of circumstances of this kind, and of others that i might mention to you, that our conclusions on and interpretations of the record are really and strictly only valid so long as we confine ourselves to one vertical section. i do not mean to tell you that there are no qualifying circumstances, so that, even in very considerable areas, we may safely speak of conformably superimposed beds being older or younger than others at many different points. but we can never be quite sure in coming to that conclusion, and especially we cannot be sure if there is any break in their continuity, or any very great distance between the points to be compared. well now, so much for the record itself,--so much for its imperfections,--so much for the conditions to be observed in interpreting it, and its chronological indications, the moment we pass beyond the limits of a vertical linear section. now let us pass from the record to that which it contains,--from the book itself to the writing and the figures on its pages. this writing and these figures consist of remains of animals and plants which, in the great majority of cases, have lived and died in the very spot in which we now find them, or at least in the immediate vicinity. you must all of you be aware--and i referred to the fact in my last lecture--that there are vast numbers of creatures living at the bottom of the sea. these creatures, like all others, sooner or later die, and their shells and hard parts lie at the bottom; and then the fine mud which is being constantly brought down by rivers and the action of the wear and tear of the sea, covers them over and protects them from any further change or alteration; and, of course, as in process of time the mud becomes hardened and solidified, the shells of these animals are preserved and firmly imbedded in the limestone or sandstone which is being thus formed. you may see in the galleries of the museum up stairs specimens of limestones in which such fossil remains of existing animals are imbedded. there are some specimens in which turtles' eggs have been imbedded in calcareous sand, and before the sun had hatched the young turtles, they became covered over with calcareous mud, and thus have been preserved and fossilized. not only does this process of imbedding and fossilization occur with marine and other aquatic animals and plants, but it affects those land animals and plants which are drifted away to sea, or become buried in bogs or morasses; and the animals which have been trodden down by their fellows and crushed in the mud at the river's bank, as the herd have come to drink. in any of these cases, the organisms may be crushed or be mutilated, before or after putrefaction, in such a manner that perhaps only a part will be left in the form in which it reaches us. it is, indeed, a most remarkable fact, that it is quite an exceptional case to find a skeleton of any one of all the thousands of wild land animals that we know are constantly being killed, or dying in the course of nature: they are preyed on and devoured by other animals or die in places where their bodies are not afterwards protected by mud. there are other animals existing in the sea, the shells of which form exceedingly large deposits. you are probably aware that before the attempt was made to lay the atlantic telegraphic cable, the government employed vessels in making a series of very careful observations and soundings of the bottom of the atlantic; and although, as we must all regret, up to the present time that project has not succeeded, we have the satisfaction of knowing that it yielded some most remarkable results to science. the atlantic ocean had to be sounded right across, to depths of several miles in some places, and the nature of its bottom was carefully ascertained. well, now, a space of about 1,000 miles wide from east to west, and i do not exactly know how many from north to south, but at any rate 600 or 700 miles, was carefully examined, and it was found that over the whole of that immense area an excessively fine chalky mud is being deposited; and this deposit is entirely made up of animals whose hard parts are deposited in this part of the ocean, and are doubtless gradually acquiring solidity and becoming metamorphosed into a chalky limestone. thus, you see, it is quite possible in this way to preserve unmistakable records of animal and vegetable life. whenever the sea-bottom, by some of those undulations of the earth's crust that i have referred to, becomes upheaved, and sections or borings are made, or pits are dug, then we become able to examine the contents and constituents of these ancient sea-bottoms, and find out what manner of animals lived at that period. now it is a very important consideration in its bearing on the completeness of the record, to inquire how far the remains contained in these fossiliferous limestones are able to convey anything like an accurate or complete account of the animals which were in existence at the time of its formation. upon that point we can form a very clear judgment, and one in which there is no possible room for any mistake. there are of course a great number of animals--such as jelly-fishes, and other animals--without any hard parts, of which we cannot reasonably expect to find any traces whatever: there is nothing of them to preserve. within a very short time, you will have noticed, after they are removed from the water, they dry up to a mere nothing; certainly they are not of a nature to leave any very visible traces of their existence on such bodies as chalk or mud. then again, look at land animals; it is, as i have said, a very uncommon thing to find a land animal entire after death. insects and other carnivorous animals very speedily pull them to pieces, putrefaction takes place, and so, out of the hundreds of thousands that are known to die every year, it is the rarest thing in the world to see one imbedded in such a way that its remains would be preserved for a lengthened period. not only is this the case, but even when animal remains have been safely imbedded, certain natural agents may wholly destroy and remove them. almost all the hard parts of animals--the bones and so on--are composed chiefly of phosphate of lime and carbonate of lime. some years ago, i had to make an inquiry into the nature of some very curious fossils sent to me from the north of scotland. fossils are usually hard bony structures that have become imbedded in the way i have described, and have gradually acquired the nature and solidity of the body with which they are associated; but in this case i had a series of 'holes' in some pieces of rock, and nothing else. those holes, however, had a certain definite shape about them, and when i got a skilful workman to make castings of the interior of these holes, i found that they were the impressions of the joints of a backbone and of the armour of a great reptile, twelve or more feet long. this great beast had died and got buried in the sand; the sand had gradually hardened over the bones, but remained porous. water had trickled through it, and that water being probably charged with a superfluity of carbonic acid, had dissolved all the phosphate and carbonate of lime, and the bones themselves had thus decayed and entirely disappeared; but as the sandstone happened to have consolidated by that time, the precise shape of the bones was retained. if that sandstone had remained soft a little longer, we should have known nothing whatsoever of the existence of the reptile whose bones it had encased. how certain it is that a vast number of animals which have existed at one period on this earth have entirely perished, and left no trace whatever of their forms, may be proved to you by other considerations. there are large tracts of sandstone in various parts of the world, in which nobody has yet found anything but footsteps. not a bone of any description, but an enormous number of traces of footsteps. there is no question about them. there is a whole valley in connecticut covered with these footsteps, and not a single fragment of the animals which made them has yet been found. let me mention another case while upon that matter, which is even more surprising than those to which i have yet referred. there is a limestone formation near oxford, at a place called stonesfield, which has yielded the remains of certain very interesting mammalian animals, and up to this time, if i recollect rightly, there have been found seven specimens of its lower jaws, and not a bit of anything else, neither limb-bones nor skull, or any part whatever; not a fragment of the whole system! of course, it would be preposterous to imagine that the beasts had nothing else but a lower jaw! the probability is, as dr. buckland showed, as the result of his observations on dead dogs in the river thames, that the lower jaw, not being secured by very firm ligaments to the bones of the head, and being a weighty affair, would easily be knocked off, or might drop away from the body as it floated in water in a state of decomposition. the jaw would thus be deposited immediately, while the rest of the body would float and drift away altogether, ultimately reaching the sea, and perhaps becoming destroyed. the jaw becomes covered up and preserved in the river silt, and thus it comes that we have such a curious circumstance as that of the lower jaws in the stonesfield slates. so that, you see, faulty as these layers of stone in the earth's crust are, defective as they necessarily are as a record, the account of contemporaneous vital phenomena presented by them is, by the necessity of the case, infinitely more defective and fragmentary. it was necessary that i should put all this very strongly before you, because, otherwise, you might have been led to think differently of the completeness of our knowledge by the next facts i shall state to you. the researches of the last three-quarters of a century have, in truth, revealed a wonderful richness of organic life in those rocks. certainly not fewer than thirty or forty thousand different species of fossils have been discovered. you have no more ground for doubting that these creatures really lived and died at or near the places in which we find them than you have for like scepticism about a shell on the sea-shore. the evidence is as good in the one case as in the other. our next business is to look at the general character of these fossil remains, and it is a subject which it will be requisite to consider carefully; and the first point for us is to examine how much the extinct 'flora' and 'fauna' as a 'whole'--disregarding altogether the 'succession' of their constituents, of which i shall speak afterwards--differ from the 'flora' and 'fauna' of the present day;--how far they differ in what we 'do' know about them, leaving altogether out of consideration speculations based upon what we 'do not' know. i strongly imagine that if it were not for the peculiar appearance that fossilised animals have, any of you might readily walk through a museum which contains fossil remains mixed up with those of the present forms of life, and i doubt very much whether your uninstructed eyes would lead you to see any vast or wonderful difference between the two. if you looked closely, you would notice, in the first place, a great many things very like animals with which you are acquainted now: you would see differences of shape and proportion, but on the whole a close similarity. i explained what i meant by orders the other day, when i described the animal kingdom as being divided in sub-kingdoms, classes and orders. if you divide the animal kingdom into orders, you will find that there are about one hundred and twenty. the number may vary on one side or the other, but this is a fair estimate. that is the sum total of the orders of all the animals which we know now, and which have been known in past times, and left remains behind. now, how many of those are absolutely extinct? that is to say, how many of these orders of animals have lived at a former period of the world's history, but have at present no representatives? that is the sense in which i meant to use the word "extinct." i mean that those animals did live on this earth at one time, but have left no one of their kind with us at the present moment. so that estimating the number of extinct animals is a sort of way of comparing the past creation as a whole with the present as a whole. among the mammalia and birds there are none extinct; but when we come to the reptiles there is a most wonderful thing: out of the eight orders, or thereabouts, which you can make among reptiles, one-half are extinct. these diagrams of the plesiosaurus, the ichthyosaurus, the pterodactyle, give you a notion of some of these extinct reptiles. and here is a cast of the pterodactyle and bones of the ichthyosaurus and the plesiosaurus, just as fresh as if it had been recently dug up in a churchyard. thus, in the reptile class, there are no less than half of the orders which are absolutely extinct. if we turn to the 'amphibia', there was one extinct order, the labyrinthodonts, typified by the large salamander-like beast shown in this diagram. no order of fishes is known to be extinct. every fish that we find in the strata--to which i have been referring--can be identified and placed in one of the orders which exist at the present day. there is not known to be a single ordinal form of insect extinct. there are only two orders extinct among the 'crustacea'. there is not known to be an extinct order of these creatures, the parasitic and other worms; but there are two, not to say three, absolutely extinct orders of this class, the 'echinodermata'; out of all the orders of the 'coelenterata' and 'protozoa' only one, the rugose corals. so that, you see, out of somewhere about 120 orders of animals, taking them altogether, you will not, at the outside estimate, find above ten or a dozen extinct. summing up all the orders of animals which have left remains behind them, you will not find above ten or a dozen which cannot be arranged with those of the present day; that is to say, that the difference does not amount to much more than ten per cent.: and the proportion of extinct orders of plants is still smaller. i think that that is a very astounding, a most astonishing fact, seeing the enormous epochs of time which have elapsed during the constitution of the surface of the earth as it at present exists; it is, indeed, a most astounding thing that the proportion of extinct ordinal types should be so exceedingly small. but now, there is another point of view in which we must look at this past creation. suppose that we were to sink a vertical pit through the floor beneath us, and that i could succeed in making a section right through in the direction of new zealand, i should find in each of the different beds through which i passed the remains of animals which i should find in that stratum and not in the others. first, i should come upon beds of gravel or drift containing the bones of large animals, such as the elephant, rhinoceros, and cave tiger. rather curious things to fall across in piccadilly! if i should dig lower still, i should come upon a bed of what we call the london clay, and in this, as you will see in our galleries upstairs, are found remains of strange cattle, remains of turtles, palms, and large tropical fruits; with shell-fish such as you see the like of now only in tropical regions. if i went below that, i should come upon the chalk, and there i should find something altogether different, the remains of ichthyosauri and pterodactyles, and ammonites, and so forth. i do not know what mr. godwin austin would say comes next, but probably rocks containing more ammonites, and more ichthyosauri and plesiosauri, with a vast number of other things; and under that i should meet with yet older rocks, containing numbers of strange shells and fishes; and in thus passing from the surface to the lowest depths of the earth's crust, the forms of animal life and vegetable life which i should meet with in the successive beds would, looking at them broadly, be the more different the further that i went down. or, in other words, inasmuch as we started with the clear principle, that in a series of naturally-disposed mud beds the lowest are the oldest, we should come to this result, that the further we go back in time the more difference exists between the animal and vegetable life of an epoch and that which now exists. that was the conclusion to which i wished to bring you at the end of this lecture. the conditions of existence as affecting the perpetuation of living beings lecture v. (of vi.), lectures to working men, at the museum of practical geology, 1863, on darwin's work: "origin of species". by thomas h. huxley in the last lecture i endeavoured to prove to you that, while, as a general rule, organic beings tend to reproduce their kind, there is in them, also, a constantly recurring tendency to vary--to vary to a greater or to a less extent. such a variety, i pointed out to you, might arise from causes which we do not understand; we therefore called it spontaneous; and it might come into existence as a definite and marked thing, without any gradations between itself and the form which preceded it. i further pointed out, that such a variety having once arisen, might be perpetuated to some extent, and indeed to a very marked extent, without any direct interference, or without any exercise of that process which we called selection. and then i stated further, that by such selection, when exercised artificially--if you took care to breed only from those forms which presented the same peculiarities of any variety which had arisen in this manner--the variation might be perpetuated, as far as we can see, indefinitely. the next question, and it is an important one for us, is this: is there any limit to the amount of variation from the primitive stock which can be produced by this process of selective breeding? in considering this question, it will be useful to class the characteristics, in respect of which organic beings vary, under two heads: we may consider structural characteristics, and we may consider physiological characteristics. in the first place, as regards structural characteristics, i endeavoured to show you, by the skeletons which i had upon the table, and by reference to a great many well-ascertained facts, that the different breeds of pigeons, the carriers, pouters, and tumblers, might vary in any of their internal and important structural characters to a very great degree; not only might there be changes in the proportions of the skull, and the characters of the feet and beaks, and so on; but that there might be an absolute difference in the number of the vertebrae of the back, as in the sacral vertebrae of the pouter; and so great is the extent of the variation in these and similar characters that i pointed out to you, by reference to the skeletons and the diagrams, that these extreme varieties may absolutely differ more from one another in their structural characters than do what naturalists call distinct species of pigeons; that is to say, that they differ so much in structure that there is a greater difference between the pouter and the tumbler than there is between such wild and distinct forms as the rock pigeon or the ring pigeon, or the ring pigeon and the stock dove; and indeed the differences are of greater value than this, for the structural differences between these domesticated pigeons are such as would be admitted by a naturalist, supposing he knew nothing at all about their origin, to entitle them to constitute even distinct genera. as i have used this term species, and shall probably use it a good deal, i had better perhaps devote a word or two to explaining what i mean by it. animals and plants are divided into groups, which become gradually smaller, beginning with a kingdom, which is divided into sub-kingdoms; then come the smaller divisions called provinces; and so on from a province to a class from a class to an order, from orders to families, and from these to genera, until we come at length to the smallest groups of animals which can be defined one from the other by constant characters, which are not sexual; and these are what naturalists call species in practice, whatever they may do in theory. if, in a state of nature, you find any two groups of living beings, which are separated one from the other by some constantly-recurring characteristic, i don't care how slight and trivial, so long as it is defined and constant, and does not depend on sexual peculiarities, then all naturalists agree in calling them two species; that is what is meant by the use of the word species--that is to say, it is, for the practical naturalist, a mere question of structural differences. [1] we have seen now--to repeat this point once more, and it is very essential that we should rightly understand it--we have seen that breeds, known to have been derived from a common stock by selection, may be as different in their structure from the original stock as species may be distinct from each other. but is the like true of the physiological characteristics of animals? do the physiological differences of varieties amount in degree to those observed between forms which naturalists call distinct species? this is a most important point for us to consider. as regards the great majority of physiological characteristics, there is no doubt that they are capable of being developed, increased, and modified by selection. there is no doubt that breeds may be made as different as species in many physiological characters. i have already pointed out to you very briefly the different habits of the breeds of pigeons, all of which depend upon their physiological peculiarities,--as the peculiar habit of tumbling, in the tumbler--the peculiarities of flight, in the "homing" birds,--the strange habit of spreading out the tail, and walking in a peculiar fashion, in the fantail,--and, lastly, the habit of blowing out the gullet, so characteristic of the pouter. these are all due to physiological modifications, and in all these respects these birds differ as much from each other as any two ordinary species do. so with dogs in their habits and instincts. it is a physiological peculiarity which leads the greyhound to chase its prey by sight,--that enables the beagle to track it by the scent,--that impels the terrier to its rat-hunting propensity,--and that leads the retriever to its habit of retrieving. these habits and instincts are all the results of physiological differences and peculiarities, which have been developed from a common stock, at least there is every reason to believe so. but it is a most singular circumstance, that while you may run through almost the whole series of physiological processes, without finding a check to your argument, you come at last to a point where you do find a check, and that is in the reproductive processes. for there is a most singular circumstance in respect to natural species--at least about some of them--and it would be sufficient for the purposes of this argument if it were true of only one of them, but there is, in fact, a great number of such cases--and that is, that, similar as they may appear to be to mere races or breeds, they present a marked peculiarity in the reproductive process. if you breed from the male and female of the same race, you of course have offspring of the like kind, and if you make the offspring breed together, you obtain the same result, and if you breed from these again, you will still have the same kind of offspring; there is no check. but if you take members of two distinct species, however similar they may be to each other and make them breed together, you will find a check, with some modifications and exceptions, however, which i shall speak of presently. if you cross two such species with each other, then,--although you may get offspring in the case of the first cross, yet, if you attempt to breed from the products of that crossing, which are what are called hybrids--that is, if you couple a male and a female hybrid--then the result is that in ninety-nine cases out of a hundred you will get no offspring at all; there will be no result whatsoever. the reason of this is quite obvious in some cases; the male hybrids, although possessing all the external appearances and characteristics of perfect animals, are physiologically imperfect and deficient in the structural parts of the reproductive elements necessary to generation. it is said to be invariably the case with the male mule, the cross between the ass and the mare; and hence it is, that, although crossing the horse with the ass is easy enough, and is constantly done, as far as i am aware, if you take two mules, a male and a female, and endeavour to breed from them, you get no offspring whatever; no generation will take place. this is what is called the sterility of the hybrids between two distinct species. you see that this is a very extraordinary circumstance; one does not see why it should be. the common teleological explanation is, that it is to prevent the impurity of the blood resulting from the crossing of one species with another, but you see it does not in reality do anything of the kind. there is nothing in this fact that hybrids cannot breed with each other, to establish such a theory; there is nothing to prevent the horse breeding with the ass, or the ass with the horse. so that this explanation breaks down, as a great many explanations of this kind do, that are only founded on mere assumptions. thus you see that there is a great difference between "mongrels," which are crosses between distinct races, and "hybrids," which are crosses between distinct species. the mongrels are, so far as we know, fertile with one another. but between species, in many cases, you cannot succeed in obtaining even the first cross: at any rate it is quite certain that the hybrids are often absolutely infertile one with another. here is a feature, then, great or small as it may be, which distinguishes natural species of animals. can we find any approximation to this in the different races known to be produced by selective breeding from a common stock? up to the present time the answer to that question is absolutely a negative one. as far as we know at present, there is nothing approximating to this check. in crossing the breeds between the fantail and the pouter, the carrier and the tumbler, or any other variety or race you may name--so far as we know at present--there is no difficulty in breeding together the mongrels. take the carrier and the fantail, for instance, and let them represent the horse and the ass in the case of distinct species; then you have, as the result of their breeding, the carrier-fantail mongrel,--we will say the male and female mongrel,--and, as far as we know, these two when crossed would not be less fertile than the original cross, or than carrier with carrier. here, you see, is a physiological contrast between the races produced by selective modification and natural species. i shall inquire into the value of this fact, and of some modifying circumstances by and by; for the present i merely put it broadly before you. but while considering this question of the limitations of species, a word must be said about what is called recurrence--the tendency of races which have been developed by selective breeding from varieties to return to their primitive type. this is supposed by many to put an absolute limit to the extent of selective and all other variations. people say, "it is all very well to talk about producing these different races, but you know very well that if you turned all these birds wild, these pouters, and carriers, and so on, they would all return to their primitive stock." this is very commonly assumed to be a fact, and it is an argument that is commonly brought forward as conclusive; but if you will take the trouble to inquire into it rather closely, i think you will find that it is not worth very much. the first question of course is, do they thus return to the primitive stock? and commonly as the thing is assumed and accepted, it is extremely difficult to get anything like good evidence of it. it is constantly said, for example, that if domesticated horses are turned wild, as they have been in some parts of asia minor and south america, that they return at once to the primitive stock from which they were bred. but the first answer that you make to this assumption is, to ask who knows what the primitive stock was; and the second answer is, that in that case the wild horses of asia minor ought to be exactly like the wild horses of south america. if they are both like the same thing, they ought manifestly to be like each other! the best authorities, however, tell you that it is quite different. the wild horse of asia is said to be of a dun colour, with a largish head, and a great many other peculiarities; while the best authorities on the wild horses of south america tell you that there is no similarity between their wild horses and those of asia minor; the cut of their heads is very different, and they are commonly chestnut or bay-coloured. it is quite clear, therefore, that as by these facts there ought to have been two primitive stocks, they go for nothing in support of the assumption that races recur to one primitive stock, and so far as this evidence is concerned, it falls to the ground. suppose for a moment that it were so, and that domesticated races, when turned wild, did return to some common condition, i cannot see that this would prove much more than that similar conditions are likely to produce similar results; and that when you take back domesticated animals into what we call natural conditions, you do exactly the same thing as if you carefully undid all the work you had gone through, for the purpose of bringing the animal from its wild to its domesticated state. i do not see anything very wonderful in the fact, if it took all that trouble to get it from a wild state, that it should go back into its original state as soon as you removed the conditions which produced the variation to the domesticated form. there is an important fact, however, forcibly brought forward by mr. darwin, which has been noticed in connection with the breeding of domesticated pigeons; and it is, that however different these breeds of pigeons may be from each other, and we have already noticed the great differences in these breeds, that if, among any of those variations, you chance to have a blue pigeon turn up, it will be sure to have the black bars across the wings, which are characteristic of the original wild stock, the rock pigeon. now, this is certainly a very remarkable circumstance; but i do not see myself how it tells very strongly either one way or the other. i think, in fact, that this argument in favour of recurrence to the primitive type might prove a great deal too much for those who so constantly bring it forward. for example, mr. darwin has very forcibly urged, that nothing is commoner than if you examine a dun horse--and i had an opportunity of verifying this illustration lately, while in the islands of the west highlands, where there are a great many dun horses--to find that horse exhibit a long black stripe down his back, very often stripes on his shoulder, and very often stripes on his legs. i, myself, saw a pony of this description a short time ago, in a baker's cart, near rothesay, in bute: it had the long stripe down the back, and stripes on the shoulders and legs, just like those of the ass, the quagga, and the zebra. now, if we interpret the theory of recurrence as applied to this case, might it not be said that here was a case of a variation exhibiting the characters and conditions of an animal occupying something like an intermediate position between the horse, the ass, the quagga, and the zebra, and from which these had been developed? in the same way with regard even to man. every anatomist will tell you that there is nothing commoner, in dissecting the human body, than to meet with what are called muscular variations--that is, if you dissect two bodies very carefully, you will probably find that the modes of attachment and insertion of the muscles are not exactly the same in both, there being great peculiarities in the mode in which the muscles are arranged; and it is very singular, that in some dissections of the human body you will come upon arrangements of the muscles very similar indeed to the same parts in the apes. is the conclusion in that case to be, that this is like the black bars in the case of the pigeon, and that it indicates a recurrence to the primitive type from which the animals have been probably developed? truly, i think that the opponents of modification and variation had better leave the argument of recurrence alone, or it may prove altogether too strong for them. to sum up,--the evidence as far as we have gone is against the argument as to any limit to divergences, so far as structure is concerned; and in favour of a physiological limitation. by selective breeding we can produce structural divergences as great as those of species, but we cannot produce equal physiological divergences. for the present i leave the question there. now, the next problem that lies before us--and it is an extremely important one--is this: does this selective breeding occur in nature? because, if there is no proof of it, all that i have been telling you goes for nothing in accounting for the origin of species. are natural causes competent to play the part of selection in perpetuating varieties? here we labour under very great difficulties. in the last lecture i had occasion to point out to you the extreme difficulty of obtaining evidence even of the first origin of those varieties which we know to have occurred in domesticated animals. i told you, that almost always the origin of these varieties is overlooked, so that i could only produce two of three cases, as that of gratio kelleia and of the ancon sheep. people forget, or do not take notice of them until they come to have a prominence; and if that is true of artificial cases, under our own eyes, and in animals in our own care, how much more difficult it must be to have at first hand good evidence of the origin of varieties in nature! indeed, i do not know that it is possible by direct evidence to prove the origin of a variety in nature, or to prove selective breeding; but i will tell you what we can prove--and this comes to the same thing--that varieties exist in nature within the limits of species, and, what is more, that when a variety has come into existence in nature, there are natural causes and conditions, which are amply competent to play the part of a selective breeder; and although that is not quite the evidence that one would like to have--though it is not direct testimony--yet it is exceeding good and exceedingly powerful evidence in its way. as to the first point, of varieties existing among natural species, i might appeal to the universal experience of every naturalist, and of any person who has ever turned any attention at all to the characteristics of plants and animals in a state of nature; but i may as well take a few definite cases, and i will begin with man himself. i am one of those who believe that, at present, there is no evidence whatever for saying, that mankind sprang originally from any more than a single pair; i must say, that i cannot see any good ground whatever, or even any tenable sort of evidence, for believing that there is more than one species of man. nevertheless, as you know, just as there are numbers of varieties in animals, so there are remarkable varieties of men. i speak not merely of those broad and distinct variations which you see at a glance. everybody, of course, knows the difference between a negro and a white man, and can tell a chinaman from an englishman. they each have peculiar characteristics of colour and physiognomy; but you must recollect that the characters of these races go very far deeper--they extend to the bony structure, and to the characters of that most important of all organs to us--the brain; so that, among men belonging to different races, or even within the same race, one man shall have a brain a third, or half, or even seventy per cent. bigger than another; and if you take the whole range of human brains, you will find a variation in some cases of a hundred per cent. apart from these variations in the size of the brain, the characters of the skull vary. thus if i draw the figures of a mongul and of a negro head on the blackboard, in the case of the last the breadth would be about seven-tenths, and in the other it would be nine-tenths of the total length. so that you see there is abundant evidence of variation among men in their natural condition. and if you turn to other animals there is just the same thing. the fox, for example, which has a very large geographical distribution all over europe, and parts of asia, and on the american continent, varies greatly. there are mostly large foxes in the north, and smaller ones in the south. in germany alone, the foresters reckon some eight different sorts. of the tiger, no one supposes that there is more than one species; they extend from the hottest parts of bengal, into the dry, cold, bitter steppes of siberia, into a latitude of 50 degrees,--so that they may even prey upon the reindeer. these tigers have exceedingly different characteristics, but still they all keep their general features, so that there is no doubt as to their being tigers. the siberian tiger has a thick fur, a small mane, and a longitudinal stripe down the back, while the tigers of java and sumatra differ in many important respects from the tigers of northern asia. so lions vary; so birds vary; and so, if you go further back and lower down in creation, you find that fishes vary. in different streams, in the same country even, you will find the trout to be quite different to each other and easily recognisable by those who fish in the particular streams. there is the same differences in leeches; leech collectors can easily point out to you the differences and the peculiarities which you yourself would probably pass by; so with fresh-water mussels; so, in fact, with every animal you can mention. in plants there is the same kind of variation. take such a case even as the common bramble. the botanists are all at war about it; some of them wanting to make out that there are many species of it, and others maintaining that they are but many varieties of one species; and they cannot settle to this day which is a species and which is a variety! so that there can be no doubt whatsoever that any plant and any animal may vary in nature; that varieties may arise in the way i have described,--as spontaneous varieties,--and that those varieties may be perpetuated in the same way that i have shown you spontaneous varieties are perpetuated; i say, therefore, that there can be no doubt as to the origin and perpetuation of varieties in nature. but the question now is:--does selection take place in nature? is there anything like the operation of man in exercising selective breeding, taking place in nature? you will observe that, at present, i say nothing about species; i wish to confine myself to the consideration of the production of those natural races which everybody admits to exist. the question is, whether in nature there are causes competent to produce races, just in the same way as man is able to produce by selection, such races of animals as we have already noticed. when a variety has arisen, the conditions of existence are such as to exercise an influence which is exactly comparable to that of artificial selection. by conditions of existence i mean two things,--there are conditions which are furnished by the physical, the inorganic world, and there are conditions of existence which are furnished by the organic world. there is, in the first place, climate; under that head i include only temperature and the varied amount of moisture of particular places. in the next place there is what is technically called station, which means--given the climate, the particular kind of place in which an animal or a plant lives or grows; for example, the station of a fish is in the water, of a fresh-water fish in fresh water; the station of a marine fish is in the sea, and a marine animal may have a station higher or deeper. so again with land animals: the differences in their stations are those of different soils and neighbourhoods; some being best adapted to a calcareous, and others to an arenaceous soil. the third condition of existence is food, by which i mean food in the broadest sense, the supply of the materials necessary to the existence of an organic being; in the case of a plant the inorganic matters, such as carbonic acid, water, ammonia, and the earthy salts or salines; in the case of the animal the inorganic and organic matters, which we have seen they require; then these are all, at least the two first, what we may call the inorganic or physical conditions of existence. food takes a mid-place, and then come the organic conditions; by which i mean the conditions which depend upon the state of the rest of the organic creation, upon the number and kind of living beings, with which an animal is surrounded. you may class these under two heads: there are organic beings, which operate as 'opponents', and there are organic beings which operate as 'helpers' to any given organic creature. the opponents may be of two kinds: there are the 'indirect opponents', which are what we may call 'rivals'; and there are the 'direct opponents', those which strive to destroy the creature; and these we call 'enemies'. by rivals i mean, of course, in the case of plants, those which require for their support the same kind of soil and station, and, among animals, those which require the same kind of station, or food, or climate; those are the indirect opponents; the direct opponents are, of course, those which prey upon an animal or vegetable. the 'helpers' may also be regarded as direct and indirect: in the case of a carnivorous animal, for example, a particular herbaceous plant may in multiplying be an indirect helper, by enabling the herbivora on which the carnivore preys to get more food, and thus to nourish the carnivore more abundantly; the direct helper may be best illustrated by reference to some parasitic creature, such as the tape-worm. the tape-worm exists in the human intestines, so that the fewer there are of men the fewer there will be of tape-worms, other things being alike. it is a humiliating reflection, perhaps, that we may be classed as direct helpers to the tape-worm, but the fact is so: we can all see that if there were no men there would be no tape-worms. it is extremely difficult to estimate, in a proper way, the importance and the working of the conditions of existence. i do not think there were any of us who had the remotest notion of properly estimating them until the publication of mr. darwin's work, which has placed them before us with remarkable clearness; and i must endeavour, as far as i can in my own fashion, to give you some notion of how they work. we shall find it easiest to take a simple case, and one as free as possible from every kind of complication. i will suppose, therefore, that all the habitable part of this globe--the dry land, amounting to about 51,000,000 square miles,--i will suppose that the whole of that dry land has the same climate, and that it is composed of the same kind of rock or soil, so that there will be the same station everywhere; we thus get rid of the peculiar influence of different climates and stations. i will then imagine that there shall be but one organic being in the world, and that shall be a plant. in this we start fair. its food is to be carbonic acid, water and ammonia, and the saline matters in the soil, which are, by the supposition, everywhere alike. we take one single plant, with no opponents, no helpers, and no rivals; it is to be a "fair field, and no favour". now, i will ask you to imagine further that it shall be a plant which shall produce every year fifty seeds, which is a very moderate number for a plant to produce; and that, by the action of the winds and currents, these seeds shall be equally and gradually distributed over the whole surface of the land. i want you now to trace out what will occur, and you will observe that i am not talking fallaciously any more than a mathematician does when he expounds his problem. if you show that the conditions of your problem are such as may actually occur in nature and do not transgress any of the known laws of nature in working out your proposition, then you are as safe in the conclusion you arrive at as is the mathematician in arriving at the solution of his problem. in science, the only way of getting rid of the complications with which a subject of this kind is environed, is to work in this deductive method. what will be the result, then? i will suppose that every plant requires one square foot of ground to live upon; and the result will be that, in the course of nine years, the plant will have occupied every single available spot in the whole globe! i have chalked upon the blackboard the figures by which i arrive at the result:-plants. plants 1 x 50 in 1st year = 50 50 x 50 " 2nd " = 2,500 2,500 x 50 " 3rd " = 125,000 125,000 x 50 " 4th " = 6,250,000 6,250,000 x 50 " 5th " = 312,500,000 312,500,000 x 50 " 6th " = 15,625,000,000 15,625,000,000 x 50 " 7th " = 781,250,000,000 781,250,000,000 x 50 " 8th " = 39,062,500,000,000 39,062,500,000,000 x 50& " 9th " = 1,953,125,000,000,000 51,000,000 sq. miles--the dry surface of the earth x 27,878,400--the number of sq. ft. in 1 sq. mile = sq. ft. 1,421,798,400,000,000 being 531,326,600,000,000 square feet less than would be required at the end of the ninth year. you will see from this that, at the end of the first year the single plant will have produced fifty more of its kind; by the end of the second year these will have increased to 2,500; and so on, in succeeding years, you get beyond even trillions; and i am not at all sure that i could tell you what the proper arithmetical denomination of the total number really is; but, at any rate, you will understand the meaning of all those noughts. then you see that, at the bottom, i have taken the 51,000,000 of square miles, constituting the surface of the dry land; and as the number of square feet are placed under and subtracted from the number of seeds that would be produced in the ninth year, you can see at once that there would be an immense number more of plants than there would be square feet of ground for their accommodation. this is certainly quite enough to prove my point; that between the eighth and ninth year after being planted the single plant would have stocked the whole available surface of the earth. this is a thing which is hardly conceivable--it seems hardly imaginable--yet it is so. it is indeed simply the law of malthus exemplified. mr. malthus was a clergyman, who worked out this subject most minutely and truthfully some years ago; he showed quite clearly,--and although he was much abused for his conclusions at the time, they have never yet been disproved and never will be--he showed that in consequence of the increase in the number of organic beings in a geometrical ratio, while the means of existence cannot be made to increase in the same ratio, that there must come a time when the number of organic beings will be in excess of the power of production of nutriment, and that thus some check must arise to the further increase of those organic beings. at the end of the ninth year we have seen that each plant would not be able to get its full square foot of ground, and at the end of another year it would have to share that space with fifty others the produce of the seeds which it would give off. what, then, takes place? every plant grows up, flourishes, occupies its square foot of ground, and gives off its fifty seeds; but notice this, that out of this number only one can come to anything; there is thus, as it were, forty-nine chances to one against its growing up; it depends upon the most fortuitous circumstances whether any one of these fifty seeds shall grow up and flourish, or whether it shall die and perish. this is what mr. darwin has drawn attention to, and called the "struggle for existence"; and i have taken this simple case of a plant because some people imagine that the phrase seems to imply a sort of fight. i have taken this plant and shown you that this is the result of the ratio of the increase, the necessary result of the arrival of a time coming for every species when exactly as many members must be destroyed as are born; that is the inevitable ultimate result of the rate of production. now, what is the result of all this? i have said that there are forty-nine struggling against every one; and it amounts to this, that the smallest possible start given to any one seed may give it an advantage which will enable it to get ahead of all the others; anything that will enable any one of these seeds to germinate six hours before any of the others will, other things being alike, enable it to choke them out altogether. i have shown you that there is no particular in which plants will not vary from each other; it is quite possible that one of our imaginary plants may vary in such a character as the thickness of the integument of its seeds; it might happen that one of the plants might produce seeds having a thinner integument, and that would enable the seeds of that plant to germinate a little quicker than those of any of the others, and those seeds would most inevitably extinguish the forty-nine times as many that were struggling with them. i have put it in this way, but you see the practical result of the process is the same as if some person had nurtured the one and destroyed the other seeds. it does not matter how the variation is produced, so long as it is once allowed to occur. the variation in the plant once fairly started tends to become hereditary and reproduce itself; the seeds would spread themselves in the same way and take part in the struggle with the forty-nine hundred, or forty-nine thousand, with which they might be exposed. thus, by degrees, this variety, with some slight organic change or modification, must spread itself over the whole surface of the habitable globe, and extirpate or replace the other kinds. that is what is meant by natural selection; that is the kind of argument by which it is perfectly demonstrable that the conditions of existence may play exactly the same part for natural varieties as man does for domesticated varieties. no one doubts at all that particular circumstances may be more favourable for one plant and less so for another, and the moment you admit that, you admit the selective power of nature. now, although i have been putting a hypothetical case, you must not suppose that i have been reasoning hypothetically. there are plenty of direct experiments which bear out what we may call the theory of natural selection; there is extremely good authority for the statement that if you take the seed of mixed varieties of wheat and sow it, collecting the seed next year and sowing it again, at length you will find that out of all your varieties only two or three have lived, or perhaps even only one. there were one or two varieties which were best fitted to get on, and they have killed out the other kinds in just the same way and with just the same certainty as if you had taken the trouble to remove them. as i have already said, the operation of nature is exactly the same as the artificial operation of man. but if this be true of that simple case, which i put before you, where there is nothing but the rivalry of one member of a species with others, what must be the operation of selective conditions, when you recollect as a matter of fact, that for every species of animal or plant there are fifty or a hundred species which might all, more or less, be comprehended in the same climate, food, and station;--that every plant has multitudinous animals which prey upon it, and which are its direct opponents; and that these have other animals preying upon them,--that every plant has its indirect helpers in the birds that scatter abroad its seed, and the animals that manure it with their dung;--i say, when these things are considered, it seems impossible that any variation which may arise in a species in nature should not tend in some way or other either to be a little better or worse than the previous stock; if it is a little better it will have an advantage over and tend to extirpate the latter in this crush and struggle; and if it is a little worse it will itself be extirpated. i know nothing that more appropriately expresses this, than the phrase, "the struggle for existence"; because it brings before your minds, in a vivid sort of way, some of the simplest possible circumstances connected with it. when a struggle is intense there must be some who are sure to be trodden down, crushed, and overpowered by others; and there will be some who just manage to get through only by the help of the slightest accident. i recollect reading an account of the famous retreat of the french troops, under napoleon, from moscow. worn out, tired, and dejected, they at length came to a great river over which there was but one bridge for the passage of the vast army. disorganised and demoralised as that army was, the struggle must certainly have been a terrible one--every one heeding only himself, and crushing through the ranks and treading down his fellows. the writer of the narrative, who was himself one of those who were fortunate enough to succeed in getting over, and not among the thousands who were left behind or forced into the river, ascribed his escape to the fact that he saw striding onward through the mass a great strong fellow,--one of the french cuirassiers, who had on a large blue cloak--and he had enough presence of mind to catch and retain a hold of this strong man's cloak. he says, "i caught hold of his cloak, and although he swore at me and cut at and struck me by turns, and at last, when he found he could not shake me off, fell to entreating me to leave go or i should prevent him from escaping, besides not assisting myself, i still kept tight hold of him, and would not quit my grasp until he had at last dragged me through." here you see was a case of selective saving--if we may so term it--depending for its success on the strength of the cloth of the cuirassier's cloak. it is the same in nature; every species has its bridge of beresina; it has to fight its way through and struggle with other species; and when well nigh overpowered, it may be that the smallest chance, something in its colour, perhaps--the minutest circumstance--will turn the scale one way or the other. suppose that by a variation of the black race it had produced the white man at any time--you know that the negroes are said to believe this to have been the case, and to imagine that cain was the first white man, and that we are his descendants--suppose that this had ever happened, and that the first residence of this human being was on the west coast of africa. there is no great structural difference between the white man and the negro, and yet there is something so singularly different in the constitution of the two, that the malarias of that country, which do not hurt the black at all, cut off and destroy the white. then you see there would have been a selective operation performed; if the white man had risen in that way, he would have been selected out and removed by means of the malaria. now there really is a very curious case of selection of this sort among pigs, and it is a case of selection of colour too. in the woods of florida there are a great many pigs, and it is a very curious thing that they are all black, every one of them. professor wyman was there some years ago, and on noticing no pigs but these black ones, he asked some of the people how it was that they had no white pigs, and the reply was that in the woods of florida there was a root which they called the paint root, and that if the white pigs were to eat any of it, it had the effect of making their hoofs crack, and they died, but if the black pigs eat any of it, it did not hurt them at all. here was a very simple case of natural selection. a skilful breeder could not more carefully develope the black breed of pigs, and weed out all the white pigs, than the paint root does. to show you how remarkably indirect may be such natural selective agencies as i have referred to, i will conclude by noticing a case mentioned by mr. darwin, and which is certainly one of the most curious of its kind. it is that of the humble bee. it has been noticed that there are a great many more humble bees in the neighbourhood of towns, than out in the open country; and the explanation of the matter is this: the humble bees build nests, in which they store their honey and deposit the larvae and eggs. the field mice are amazingly fond of the honey and larvae; therefore, wherever there are plenty of field mice, as in the country, the humble bees are kept down; but in the neighbourhood of towns, the number of cats which prowl about the fields eat up the field mice, and of course the more mice they eat up the less there are to prey upon the larvae of the bees--the cats are therefore the indirect helpers of the bees! [2] coming back a step farther we may say that the old maids are also indirect friends of the humble bees, and indirect enemies of the field mice, as they keep the cats which eat up the latter! this is an illustration somewhat beneath the dignity of the subject, perhaps, but it occurs to me in passing, and with it i will conclude this lecture. [footnote 1: i lay stress here on the 'practical' signification of "species." whether a physiological test between species exist or not, it is hardly ever applicable by the practical naturalist.] [footnote 2: the humble bees, on the other hand, are direct helpers of some plants, such as the heartsease and red clover, which are fertilized by the visits of the bees; and they are indirect helpers of the numerous insects which are more or less completely supported by the heartsease and red clover.] the method by which the causes of the present and past conditions of organic nature are to be discovered.--the origination of living beings lecture iii. (of vi.), lectures to working men, at the museum of practical geology, 1863, on darwin's work: "origin of species". by thomas h. huxley in the two preceding lectures i have endeavoured to indicate to you the extent of the subject-matter of the inquiry upon which we are engaged; and now, having thus acquired some conception of the past and present phenomena of organic nature, i must now turn to that which constitutes the great problem which we have set before ourselves;--i mean, the question of what knowledge we have of the causes of these phenomena of organic nature, and how such knowledge is obtainable. here, on the threshold of the inquiry, an objection meets us. there are in the world a number of extremely worthy, well-meaning persons, whose judgments and opinions are entitled to the utmost respect on account of their sincerity, who are of opinion that vital phenomena, and especially all questions relating to the origin of vital phenomena, are questions quite apart from the ordinary run of inquiry, and are, by their very nature, placed out of our reach. they say that all these phenomena originated miraculously, or in some way totally different from the ordinary course of nature, and that therefore they conceive it to be futile, not to say presumptuous, to attempt to inquire into them. to such sincere and earnest persons, i would only say, that a question of this kind is not to be shelved upon theoretical or speculative grounds. you may remember the story of the sophist who demonstrated to diogenes in the most complete and satisfactory manner that he could not walk; that, in fact, all motion was an impossibility; and that diogenes refuted him by simply getting up and walking round his tub. so, in the same way, the man of science replies to objections of this kind, by simply getting up and walking onward, and showing what science has done and is doing--by pointing to that immense mass of facts which have been ascertained and systematized under the forms of the great doctrines of morphology, of development, of distribution, and the like. he sees an enormous mass of facts and laws relating to organic beings, which stand on the same good sound foundation as every other natural law; and therefore, with this mass of facts and laws before us, therefore, seeing that, as far as organic matters have hitherto been accessible and studied, they have shown themselves capable of yielding to scientific investigation, we may accept this as proof that order and law reign there as well as in the rest of nature; and the man of science says nothing to objectors of this sort, but supposes that we can and shall walk to a knowledge of the origin of organic nature, in the same way that we have walked to a knowledge of the laws and principles of the inorganic world. but there are objectors who say the same from ignorance and ill-will. to such i would reply that the objection comes ill from them, and that the real presumption, i may almost say the real blasphemy, in this matter, is in the attempt to limit that inquiry into the causes of phenomena which is the source of all human blessings, and from which has sprung all human prosperity and progress; for, after all, we can accomplish comparatively little; the limited range of our own faculties bounds us on every side,--the field of our powers of observation is small enough, and he who endeavours to narrow the sphere of our inquiries is only pursuing a course that is likely to produce the greatest harm to his fellow-men. but now, assuming, as we all do, i hope, that these phenomena are properly accessible to inquiry, and setting out upon our search into the causes of the phenomena of organic nature, or, at any rate, setting out to discover how much we at present know upon these abstruse matters, the question arises as to what is to be our course of proceeding, and what method we must lay down for our guidance. i reply to that question, that our method must be exactly the same as that which is pursued in any other scientific inquiry, the method of scientific investigation being the same for all orders of facts and phenomena whatsoever. i must dwell a little on this point, for i wish you to leave this room with a very clear conviction that scientific investigation is not, as many people seem to suppose, some kind of modern black art. i say that you might easily gather this impression from the manner in which many persons speak of scientific inquiry, or talk about inductive and deductive philosophy, or the principles of the "baconian philosophy." i do protest that, of the vast number of cants in this world, there are none, to my mind, so contemptible as the pseudoscientific cant which is talked about the "baconian philosophy." to hear people talk about the great chancellor--and a very great man he certainly was,--you would think that it was he who had invented science, and that there was no such thing as sound reasoning before the time of queen elizabeth. of course you say, that cannot possibly be true; you perceive, on a moment's reflection, that such an idea is absurdly wrong, and yet, so firmly rooted is this sort of impression,--i cannot call it an idea, or conception,--the thing is too absurd to be entertained,--but so completely does it exist at the bottom of most men's minds, that this has been a matter of observation with me for many years past. there are many men who, though knowing absolutely nothing of the subject with which they may be dealing, wish, nevertheless, to damage the author of some view with which they think fit to disagree. what they do, then, is not to go and learn something about the subject, which one would naturally think the best way of fairly dealing with it; but they abuse the originator of the view they question, in a general manner, and wind up by saying that, "after all, you know, the principles and method of this author are totally opposed to the canons of the baconian philosophy." then everybody applauds, as a matter of course, and agrees that it must be so. but if you were to stop them all in the middle of their applause, you would probably find that neither the speaker nor his applauders could tell you how or in what way it was so; neither the one nor the other having the slightest idea of what they mean when they speak of the "baconian philosophy." you will understand, i hope, that i have not the slightest desire to join in the outcry against either the morals, the intellect, or the great genius of lord chancellor bacon. he was undoubtedly a very great man, let people say what they will of him; but notwithstanding all that he did for philosophy, it would be entirely wrong to suppose that the methods of modern scientific inquiry originated with him, or with his age; they originated with the first man, whoever he was; and indeed existed long before him, for many of the essential processes of reasoning are exerted by the higher order of brutes as completely and effectively as by ourselves. we see in many of the brute creation the exercise of one, at least, of the same powers of reasoning as that which we ourselves employ. the method of scientific investigation is nothing but the expression of the necessary mode of working of the human mind. it is simply the mode at which all phenomena are reasoned about, rendered precise and exact. there is no more difference, but there is just the same kind of difference, between the mental operations of a man of science and those of an ordinary person, as there is between the operations and methods of a baker or of a butcher weighing out his goods in common scales, and the operations of a chemist in performing a difficult and complex analysis by means of his balance and finely-graduated weights. it is not that the action of the scales in the one case, and the balance in the other, differ in the principles of their construction or manner of working; but the beam of one is set on an infinitely finer axis than the other, and of course turns by the addition of a much smaller weight. you will understand this better, perhaps, if i give you some familiar example. you have all heard it repeated, i dare say, that men of science work by means of induction and deduction, and that by the help of these operations, they, in a sort of sense, wring from nature certain other things, which are called natural laws, and causes, and that out of these, by some cunning skill of their own, they build up hypotheses and theories. and it is imagined by many, that the operations of the common mind can be by no means compared with these processes, and that they have to be acquired by a sort of special apprenticeship to the craft. to hear all these large words, you would think that the mind of a man of science must be constituted differently from that of his fellow men; but if you will not be frightened by terms, you will discover that you are quite wrong, and that all these terrible apparatus are being used by yourselves every day and every hour of your lives. there is a well-known incident in one of moliere's plays, where the author makes the hero express unbounded delight on being told that he had been talking prose during the whole of his life. in the same way, i trust, that you will take comfort, and be delighted with yourselves, on the discovery that you have been acting on the principles of inductive and deductive philosophy during the same period. probably there is not one here who has not in the course of the day had occasion to set in motion a complex train of reasoning, of the very same kind, though differing of course in degree, as that which a scientific man goes through in tracing the causes of natural phenomena. a very trivial circumstance will serve to exemplify this. suppose you go into a fruiterer's shop, wanting an apple,--you take up one, and, on biting it, you find it is sour; you look at it, and see that it is hard and green. you take up another one, and that too is hard, green, and sour. the shopman offers you a third; but, before biting it, you examine it, and find that it is hard and green, and you immediately say that you will not have it, as it must be sour, like those that you have already tried. nothing can be more simple than that, you think; but if you will take the trouble to analyze and trace out into its logical elements what has been done by the mind, you will be greatly surprised. in the first place, you have performed the operation of induction. you found that, in two experiences, hardness and greenness in apples go together with sourness. it was so in the first case, and it was confirmed by the second. true, it is a very small basis, but still it is enough to make an induction from; you generalize the facts, and you expect to find sourness in apples where you get hardness and greenness. you found upon that a general law, that all hard and green apples are sour; and that, so far as it goes, is a perfect induction. well, having got your natural law in this way, when you are offered another apple which you find is hard and green, you say, "all hard and green apples are sour; this apple is hard and green, therefore this apple is sour." that train of reasoning is what logicians call a syllogism, and has all its various parts and terms,--its major premiss, its minor premiss, and its conclusion. and, by the help of further reasoning, which, if drawn out, would have to be exhibited in two or three other syllogisms, you arrive at your final determination, "i will not have that apple." so that, you see, you have, in the first place, established a law by induction, and upon that you have founded a deduction, and reasoned out the special conclusion of the particular case. well now, suppose, having got your law, that at some time afterwards, you are discussing the qualities of apples with a friend: you will say to him, "it is a very curious thing,--but i find that all hard and green apples are sour!" your friend says to you, "but how do you know that?" you at once reply, "oh, because i have tried it over and over again, and have always found them to be so." well, if we were talking science instead of common sense, we should call that an experimental verification. and, if still opposed, you go further, and say, "i have heard from the people in somersetshire and devonshire, where a large number of apples are grown, that they have observed the same thing. it is also found to be the case in normandy, and in north america. in short, i find it to be the universal experience of mankind wherever attention has been directed to the subject." whereupon, your friend, unless he is a very unreasonable man, agrees with you, and is convinced that you are quite right in the conclusion you have drawn. he believes, although perhaps he does not know he believes it, that the more extensive verifications are,--that the more frequently experiments have been made, and results of the same kind arrived at,--that the more varied the conditions under which the same results have been attained, the more certain is the ultimate conclusion, and he disputes the question no further. he sees that the experiment has been tried under all sorts of conditions, as to time, place, and people, with the same result; and he says with you, therefore, that the law you have laid down must be a good one, and he must believe it. in science we do the same thing;--the philosopher exercises precisely the same faculties, though in a much more delicate manner. in scientific inquiry it becomes a matter of duty to expose a supposed law to every possible kind of verification, and to take care, moreover, that this is done intentionally, and not left to a mere accident, as in the case of the apples. and in science, as in common life, our confidence in a law is in exact proportion to the absence of variation in the result of our experimental verifications. for instance, if you let go your grasp of an article you may have in your hand, it will immediately fall to the ground. that is a very common verification of one of the best established laws of nature--that of gravitation. the method by which men of science establish the existence of that law is exactly the same as that by which we have established the trivial proposition about the sourness of hard and green apples. but we believe it in such an extensive, thorough, and unhesitating manner because the universal experience of mankind verifies it, and we can verify it ourselves at any time; and that is the strongest possible foundation on which any natural law can rest. so much by way of proof that the method of establishing laws in science is exactly the same as that pursued in common life. let us now turn to another matter (though really it is but another phase of the same question), and that is, the method by which, from the relations of certain phenomena, we prove that some stand in the position of causes towards the others. i want to put the case clearly before you, and i will therefore show you what i mean by another familiar example. i will suppose that one of you, on coming down in the morning to the parlour of your house, finds that a tea-pot and some spoons which had been left in the room on the previous evening are gone,--the window is open, and you observe the mark of a dirty hand on the window-frame, and perhaps, in addition to that, you notice the impress of a hob-nailed shoe on the gravel outside. all these phenomena have struck your attention instantly, and before two minutes have passed you say, "oh, somebody has broken open the window, entered the room, and run off with the spoons and the tea-pot!" that speech is out of your mouth in a moment. and you will probably add, "i know there has; i am quite sure of it!" you mean to say exactly what you know; but in reality what you have said has been the expression of what is, in all essential particulars, an hypothesis. you do not 'know' it at all; it is nothing but an hypothesis rapidly framed in your own mind! and it is an hypothesis founded on a long train of inductions and deductions. what are those inductions and deductions, and how have you got at this hypothesis? you have observed, in the first place, that the window is open; but by a train of reasoning involving many inductions and deductions, you have probably arrived long before at the general law--and a very good one it is--that windows do not open of themselves; and you therefore conclude that something has opened the window. a second general law that you have arrived at in the same way is, that tea-pots and spoons do not go out of a window spontaneously, and you are satisfied that, as they are not now where you left them, they have been removed. in the third place, you look at the marks on the window-sill, and the shoemarks outside, and you say that in all previous experience the former kind of mark has never been produced by anything else but the hand of a human being; and the same experience shows that no other animal but man at present wears shoes with hob-nails on them such as would produce the marks in the gravel. i do not know, even if we could discover any of those "missing links" that are talked about, that they would help us to any other conclusion! at any rate the law which states our present experience is strong enough for my present purpose.--you next reach the conclusion, that as these kinds of marks have not been left by any other animals than men, or are liable to be formed in any other way than by a man's hand and shoe, the marks in question have been formed by a man in that way. you have, further, a general law, founded on observation and experience, and that, too, is, i am sorry to say, a very universal and unimpeachable one,--that some men are thieves; and you assume at once from all these premisses--and that is what constitutes your hypothesis--that the man who made the marks outside and on the window-sill, opened the window, got into the room, and stole your tea-pot and spoons. you have now arrived at a 'vera causa';--you have assumed a cause which it is plain is competent to produce all the phenomena you have observed. you can explain all these phenomena only by the hypothesis of a thief. but that is a hypothetical conclusion, of the justice of which you have no absolute proof at all; it is only rendered highly probable by a series of inductive and deductive reasonings. i suppose your first action, assuming that you are a man of ordinary common sense, and that you have established this hypothesis to your own satisfaction, will very likely be to go off for the police, and set them on the track of the burglar, with the view to the recovery of your property. but just as you are starting with this object, some person comes in, and on learning what you are about, says, "my good friend, you are going on a great deal too fast. how do you know that the man who really made the marks took the spoons? it might have been a monkey that took them, and the man may have merely looked in afterwards." you would probably reply, "well, that is all very well, but you see it is contrary to all experience of the way tea-pots and spoons are abstracted; so that, at any rate, your hypothesis is less probable than mine." while you are talking the thing over in this way, another friend arrives, one of that good kind of people that i was talking of a little while ago. and he might say, "oh, my dear sir, you are certainly going on a great deal too fast. you are most presumptuous. you admit that all these occurrences took place when you were fast asleep, at a time when you could not possibly have known anything about what was taking place. how do you know that the laws of nature are not suspended during the night? it may be that there has been some kind of supernatural interference in this case." in point of fact, he declares that your hypothesis is one of which you cannot at all demonstrate the truth, and that you are by no means sure that the laws of nature are the same when you are asleep as when you are awake. well, now, you cannot at the moment answer that kind of reasoning. you feel that your worthy friend has you somewhat at a disadvantage. you will feel perfectly convinced in your own mind, however, that you are quite right, and you say to him, "my good friend, i can only be guided by the natural probabilities of the case, and if you will be kind enough to stand aside and permit me to pass, i will go and fetch the police." well, we will suppose that your journey is successful, and that by good luck you meet with a policeman; that eventually the burglar is found with your property on his person, and the marks correspond to his hand and to his boots. probably any jury would consider those facts a very good experimental verification of your hypothesis, touching the cause of the abnormal phenomena observed in your parlour, and would act accordingly. now, in this suppositious case, i have taken phenomena of a very common kind, in order that you might see what are the different steps in an ordinary process of reasoning, if you will only take the trouble to analyse it carefully. all the operations i have described, you will see, are involved in the mind of any man of sense in leading him to a conclusion as to the course he should take in order to make good a robbery and punish the offender. i say that you are led, in that case, to your conclusion by exactly the same train of reasoning as that which a man of science pursues when he is endeavouring to discover the origin and laws of the most occult phenomena. the process is, and always must be, the same; and precisely the same mode of reasoning was employed by newton and laplace in their endeavours to discover and define the causes of the movements of the heavenly bodies, as you, with your own common sense, would employ to detect a burglar. the only difference is, that the nature of the inquiry being more abstruse, every step has to be most carefully watched, so that there may not be a single crack or flaw in your hypothesis. a flaw or crack in many of the hypotheses of daily life may be of little or no moment as affecting the general correctness of the conclusions at which we may arrive; but, in a scientific inquiry, a fallacy, great or small, is always of importance, and is sure to be constantly productive of mischievous, if not fatal results. do not allow yourselves to be misled by the common notion that an hypothesis is untrustworthy simply because it is an hypothesis. it is often urged, in respect to some scientific conclusion, that, after all, it is only an hypothesis. but what more have we to guide us in nine-tenths of the most important affairs of daily life than hypotheses, and often very ill-based ones? so that in science, where the evidence of an hypothesis is subjected to the most rigid examination, we may rightly pursue the same course. you may have hypotheses and hypotheses. a man may say, if he likes, that the moon is made of green cheese: that is an hypothesis. but another man, who has devoted a great deal of time and attention to the subject, and availed himself of the most powerful telescopes and the results of the observations of others, declares that in his opinion it is probably composed of materials very similar to those of which our own earth is made up: and that is also only an hypothesis. but i need not tell you that there is an enormous difference in the value of the two hypotheses. that one which is based on sound scientific knowledge is sure to have a corresponding value; and that which is a mere hasty random guess is likely to have but little value. every great step in our progress in discovering causes has been made in exactly the same way as that which i have detailed to you. a person observing the occurrence of certain facts and phenomena asks, naturally enough, what process, what kind of operation known to occur in nature applied to the particular case, will unravel and explain the mystery? hence you have the scientific hypothesis; and its value will be proportionate to the care and completeness with which its basis had been tested and verified. it is in these matters as in the commonest affairs of practical life: the guess of the fool will be folly, while the guess of the wise man will contain wisdom. in all cases, you see that the value of the result depends on the patience and faithfulness with which the investigator applies to his hypothesis every possible kind of verification. i dare say i may have to return to this point by-and-by; but having dealt thus far with our logical methods, i must now turn to something which, perhaps, you may consider more interesting, or, at any rate, more tangible. but in reality there are but few things that can be more important for you to understand than the mental processes and the means by which we obtain scientific conclusions and theories. [1] having granted that the inquiry is a proper one, and having determined on the nature of the methods we are to pursue and which only can lead to success, i must now turn to the consideration of our knowledge of the nature of the processes which have resulted in the present condition of organic nature. here, let me say at once, lest some of you misunderstand me, that i have extremely little to report. the question of how the present condition of organic nature came about, resolves itself into two questions. the first is: how has organic or living matter commenced its existence? and the second is: how has it been perpetuated? on the second question i shall have more to say hereafter. but on the first one, what i now have to say will be for the most part of a negative character. if you consider what kind of evidence we can have upon this matter, it will resolve itself into two kinds. we may have historical evidence and we may have experimental evidence. it is, for example, conceivable, that inasmuch as the hardened mud which forms a considerable portion of the thickness of the earth's crust contains faithful records of the past forms of life, and inasmuch as these differ more and more as we go further down,--it is possible and conceivable that we might come to some particular bed or stratum which should contain the remains of those creatures with which organic life began upon the earth. and if we did so, and if such forms of organic life were preservable, we should have what i would call historical evidence of the mode in which organic life began upon this planet. many persons will tell you, and indeed you will find it stated in many works on geology, that this has been done, and that we really possess such a record; there are some who imagine that the earliest forms of life of which we have as yet discovered any record, are in truth the forms in which animal life began upon the globe. the grounds on which they base that supposition are these:--that if you go through the enormous thickness of the earth's crust and get down to the older rocks, the higher vertebrate animals--the quadrupeds, birds, and fishes--cease to be found; beneath them you find only the invertebrate animals; and in the deepest and lowest rocks those remains become scantier and scantier, not in any very gradual progression, however, until, at length, in what are supposed to be the oldest rocks, the animal remains which are found are almost always confined to four forms--'oldhamia', whose precise nature is not known, whether plant or animal; 'lingula', a kind of mollusc; 'trilobites', a crustacean animal, having the same essential plan of construction, though differing in many details from a lobster or crab; and hymenocaris, which is also a crustacean. so that you have all the 'fauna' reduced, at this period, to four forms: one a kind of animal or plant that we know nothing about, and three undoubted animals--two crustaceans and one mollusc. i think, considering the organization of these mollusca and crustacea, and looking at their very complex nature, that it does indeed require a very strong imagination to conceive that these were the first created of all living things. and you must take into consideration the fact that we have not the slightest proof that these which we call the oldest beds are really so: i repeat, we have not the slightest proof of it. when you find in some places that in an enormous thickness of rocks there are but very scanty traces of life, or absolutely none at all; and that in other parts of the world rocks of the very same formation are crowded with the records of living forms, i think it is impossible to place any reliance on the supposition, or to feel oneself justified in supposing that these are the forms in which life first commenced. i have not time here to enter upon the technical grounds upon which i am led to this conclusion,--that could hardly be done properly in half a dozen lectures on that part alone;--i must content myself with saying that i do not at all believe that these are the oldest forms of life. i turn to the experimental side to see what evidence we have there. to enable us to say that we know anything about the experimental origination of organization and life, the investigator ought to be able to take inorganic matters, such as carbonic acid, ammonia, water, and salines, in any sort of inorganic combination, and be able to build them up into protein matter, and that that protein matter ought to begin to live in an organic form. that, nobody has done as yet, and i suspect it will be a long while before anybody does do it. but the thing is by no means so impossible as it looks; for the researches of modern chemistry have shown us--i won't say the road towards it, but, if i may so say, they have shown the finger-post pointing to the road that may lead to it. it is not many years ago--and you must recollect that organic chemistry is a young science, not above a couple of generations old,--you must not expect too much of it; it is not many years ago since it was said to be perfectly impossible to fabricate any organic compound; that is to say, any non-mineral compound which is to be found in an organized being. it remained so for a very long period; but it is now a considerable number of years since a distinguished foreign chemist contrived to fabricate urea, a substance of a very complex character, which forms one of the waste products of animal structures. and of late years a number of other compounds, such as butyric acid, and others, have been added to the list. i need not tell you that chemistry is an enormous distance from the goal i indicate; all i wish to point out to you is, that it is by no means safe to say that that goal may not be reached one day. it may be that it is impossible for us to produce the conditions requisite to the origination of life; but we must speak modestly about the matter, and recollect that science has put her foot upon the bottom round of the ladder. truly he would be a bold man who would venture to predict where she will be fifty years hence. there is another inquiry which bears indirectly upon this question, and upon which i must say a few words. you are all of you aware of the phenomena of what is called spontaneous generation. our forefathers, down to the seventeenth century, or thereabouts, all imagined, in perfectly good faith, that certain vegetable and animal forms gave birth, in the process of their decomposition, to insect life. thus, if you put a piece of meat in the sun, and allowed it to putrefy, they conceived that the grubs which soon began to appear were the result of the action of a power of spontaneous generation which the meat contained. and they could give you receipts for making various animal and vegetable preparations which would produce particular kinds of animals. a very distinguished italian naturalist, named redi, took up the question, at a time when everybody believed in it; among others our own great harvey, the discoverer of the circulation of the blood. you will constantly find his name quoted, however, as an opponent of the doctrine of spontaneous generation; but the fact is, and you will see it if you will take the trouble to look into his works, harvey believed it as profoundly as any man of his time; but he happened to enunciate a very curious proposition--that every living thing came from an 'egg'; he did not mean to use the word in the sense in which we now employ it, he only meant to say that every living thing originated in a little rounded particle of organized substance; and it is from this circumstance, probably, that the notion of harvey having opposed the doctrine originated. then came redi, and he proceeded to upset the doctrine in a very simple manner. he merely covered the piece of meat with some very fine gauze, and then he exposed it to the same conditions. the result of this was that no grubs or insects were produced; he proved that the grubs originated from the insects who came and deposited their eggs in the meat, and that they were hatched by the heat of the sun. by this kind of inquiry he thoroughly upset the doctrine of spontaneous generation, for his time at least. then came the discovery and application of the microscope to scientific inquiries, which showed to naturalists that besides the organisms which they already knew as living beings and plants, there were an immense number of minute things which could be obtained apparently almost at will from decaying vegetable and animal forms. thus, if you took some ordinary black pepper or some hay, and steeped it in water, you would find in the course of a few days that the water had become impregnated with an immense number of animalcules swimming about in all directions. from facts of this kind naturalists were led to revive the theory of spontaneous generation. they were headed here by an english naturalist,--needham,--and afterwards in france by the learned buffon. they said that these things were absolutely begotten in the water of the decaying substances out of which the infusion was made. it did not matter whether you took animal or vegetable matter, you had only to steep it in water and expose it, and you would soon have plenty of animalcules. they made an hypothesis about this which was a very fair one. they said, this matter of the animal world, or of the higher plants, appears to be dead, but in reality it has a sort of dim life about it, which, if it is placed under fair conditions, will cause it to break up into the forms of these little animalcules, and they will go through their lives in the same way as the animal or plant of which they once formed a part. the question now became very hotly debated. spallanzani, an italian naturalist, took up opposite views to those of needham and buffon, and by means of certain experiments he showed that it was quite possible to stop the process by boiling the water, and closing the vessel in which it was contained. "oh!" said his opponents; "but what do you know you may be doing when you heat the air over the water in this way? you may be destroying some property of the air requisite for the spontaneous generation of the animalcules." however, spallanzani's views were supposed to be upon the right side, and those of the others fell into discredit; although the fact was that spallanzani had not made good his views. well, then, the subject continued to be revived from time to time, and experiments were made by several persons; but these experiments were not altogether satisfactory. it was found that if you put an infusion in which animalcules would appear if it were exposed to the air into a vessel and boiled it, and then sealed up the mouth of the vessel, so that no air, save such as had been heated to 212 degrees, could reach its contents, that then no animalcules would be found; but if you took the same vessel and exposed the infusion to the air, then you would get animalcules. furthermore, it was found that if you connected the mouth of the vessel with a red-hot tube in such a way that the air would have to pass through the tube before reaching the infusion, that then you would get no animalcules. yet another thing was noticed: if you took two flasks containing the same kind of infusion, and left one entirely exposed to the air, and in the mouth of the other placed a ball of cotton wool, so that the air would have to filter itself through it before reaching the infusion, that then, although you might have plenty of animalcules in the first flask, you would certainly obtain none from the second. these experiments, you see, all tended towards one conclusion--that the infusoria were developed from little minute spores or eggs which were constantly floating in the atmosphere, which lose their power of germination if subjected to heat. but one observer now made another experiment which seemed to go entirely the other way, and puzzled him altogether. he took some of this boiled infusion that i have been speaking of, and by the use of a mercurial bath--a kind of trough used in laboratories--he deftly inverted a vessel containing the infusion into the mercury, so that the latter reached a little beyond the level of the mouth of the 'inverted' vessel. you see that he thus had a quantity of the infusion shut off from any possible communication with the outer air by being inverted upon a bed of mercury. he then prepared some pure oxygen and nitrogen gases, and passed them by means of a tube going from the outside of the vessel, up through the mercury into the infusion; so that he thus had it exposed to a perfectly pure atmosphere of the same constituents as the external air. of course, he expected he would get no infusorial animalcules at all in that infusion; but, to his great dismay and discomfiture, he found he almost always did get them. furthermore, it has been found that experiments made in the manner described above answer well with most infusions; but that if you fill the vessel with boiled milk, and then stop the neck with cotton-wool, you 'will' have infusoria. so that you see there were two experiments that brought you to one kind of conclusion, and three to another; which was a most unsatisfactory state of things to arrive at in a scientific inquiry. some few years after this, the question began to be very hotly discussed in france. there was m. pouchet, a professor at rouen, a very learned man, but certainly not a very rigid experimentalist. he published a number of experiments of his own, some of which were very ingenious, to show that if you went to work in a proper way, there was a truth in the doctrine of spontaneous generation. well, it was one of the most fortunate things in the world that m. pouchet took up this question, because it induced a distinguished french chemist, m. pasteur, to take up the question on the other side; and he has certainly worked it out in the most perfect manner. i am glad to say, too, that he has published his researches in time to enable me to give you an account of them. he verified all the experiments which i have just mentioned to you--and then finding those extraordinary anomalies, as in the case of the mercury bath and the milk, he set himself to work to discover their nature. in the case of milk he found it to be a question of temperature. milk in a fresh state is slightly alkaline; and it is a very curious circumstance, but this very slight degree of alkalinity seems to have the effect of preserving the organisms which fall into it from the air from being destroyed at a temperature of 212 degrees, which is the boiling point. but if you raise the temperature 10 degrees when you boil it, the milk behaves like everything else; and if the air with which it comes in contact, after being boiled at this temperature, is passed through a red-hot tube, you will not get a trace of organisms. he then turned his attention to the mercury bath, and found on examination that the surface of the mercury was almost always covered with a very fine dust. he found that even the mercury itself was positively full of organic matters; that from being constantly exposed to the air, it had collected an immense number of these infusorial organisms from the air. well, under these circumstances he felt that the case was quite clear, and that the mercury was not what it had appeared to m. schwann to be,--a bar to the admission of these organisms; but that, in reality, it acted as a reservoir from which the infusion was immediately supplied with the large quantity that had so puzzled him. but not content with explaining the experiments of others, m. pasteur went to work to satisfy himself completely. he said to himself: "if my view is right, and if, in point of fact, all these appearances of spontaneous generation are altogether due to the falling of minute germs suspended in the atmosphere,--why, i ought not only to be able to show the germs, but i ought to be able to catch and sow them, and produce the resulting organisms." he, accordingly, constructed a very ingenious apparatus to enable him to accomplish this trapping of this "germ dust" in the air. he fixed in the window of his room a glass tube, in the centre of which he had placed a ball of gun-cotton, which, as you all know, is ordinary cotton-wool, which, from having been steeped in strong acid, is converted into a substance of great explosive power. it is also soluble in alcohol and ether. one end of the glass tube was, of course, open to the external air; and at the other end of it he placed an aspirator, a contrivance for causing a current of the external air to pass through the tube. he kept this apparatus going for four-and-twenty hours, and then removed the 'dusted' gun-cotton, and dissolved it in alcohol and ether. he then allowed this to stand for a few hours, and the result was, that a very fine dust was gradually deposited at the bottom of it. that dust, on being transferred to the stage of a microscope, was found to contain an enormous number of starch grains. you know that the materials of our food and the greater portion of plants are composed of starch, and we are constantly making use of it in a variety of ways, so that there is always a quantity of it suspended in the air. it is these starch grains which form many of those bright specks that we see dancing in a ray of light sometimes. but besides these, m. pasteur found also an immense number of other organic substances such as spores of fungi, which had been floating about in the air and had got caged in this way. he went farther, and said to himself, "if these really are the things that give rise to the appearance of spontaneous generation, i ought to be able to take a ball of this 'dusted' gun-cotton and put it into one of my vessels, containing that boiled infusion which has been kept away from the air, and in which no infusoria are at present developed, and then, if i am right, the introduction of this gun-cotton will give rise to organisms." accordingly, he took one of these vessels of infusion, which had been kept eighteen months, without the least appearance of life, and by a most ingenious contrivance, he managed to break it open and introduce such a ball of gun-cotton, without allowing the infusion or the cotton ball to come into contact with any air but that which had been subjected to a red heat, and in twenty-four hours he had the satisfaction of finding all the indications of what had been hitherto called spontaneous generation. he had succeeded in catching the germs and developing organisms in the way he had anticipated. it now struck him that the truth of his conclusions might be demonstrated without all the apparatus he had employed. to do this, he took some decaying animal or vegetable substance, such as urine, which is an extremely decomposable substance, or the juice of yeast, or perhaps some other artificial preparation, and filled a vessel having a long tubular neck with it. he then boiled the liquid and bent that long neck into an s shape or zig-zag, leaving it open at the end. the infusion then gave no trace of any appearance of spontaneous generation, however long it might be left, as all the germs in the air were deposited in the beginning of the bent neck. he then cut the tube close to the vessel, and allowed the ordinary air to have free and direct access; and the result of that was the appearance of organisms in it, as soon as the infusion had been allowed to stand long enough to allow of the growth of those it received from the air, which was about forty-eight hours. the result of m. pasteur's experiments proved, therefore, in the most conclusive manner, that all the appearances of spontaneous generation arose from nothing more than the deposition of the germs of organisms which were constantly floating in the air. to this conclusion, however, the objection was made, that if that were the cause, then the air would contain such an enormous number of these germs, that it would be a continual fog. but m. pasteur replied that they are not there in anything like the number we might suppose, and that an exaggerated view has been held on that subject; he showed that the chances of animal or vegetable life appearing in infusions, depend entirely on the conditions under which they are exposed. if they are exposed to the ordinary atmosphere around us, why, of course, you may have organisms appearing early. but, on the other hand, if they are exposed to air from a great height, or from some very quiet cellar, you will often not find a single trace of life. so that m. pasteur arrived at last at the clear and definite result, that all these appearances are like the case of the worms in the piece of meat, which was refuted by redi, simply germs carried by the air and deposited in the liquids in which they afterwards appear. for my own part, i conceive that, with the particulars of m. pasteur's experiments before us, we cannot fail to arrive at his conclusions; and that the doctrine of spontaneous generation has received a final 'coup de grace'. you, of course, understand that all this in no way interferes with the 'possibility' of the fabrication of organic matters by the direct method to which i have referred, remote as that possibility may be. [footnote 1: those who wish to study fully the doctrines of which i have endeavoured to give some rough and ready illustrations, must read mr. john stuart mill's 'system of logic'.] on the reception of the 'origin of species' by professor thomas henry huxley from the life and letters of charles darwin edited by francis darwin on the reception of the 'origin of species.' to the present generation, that is to say, the people a few years on the hither and thither side of thirty, the name of charles darwin stands alongside of those of isaac newton and michael faraday; and, like them, calls up the grand ideal of a searcher after truth and interpreter of nature. they think of him who bore it as a rare combination of genius, industry, and unswerving veracity, who earned his place among the most famous men of the age by sheer native power, in the teeth of a gale of popular prejudice, and uncheered by a sign of favour or appreciation from the official fountains of honour; as one who in spite of an acute sensitiveness to praise and blame, and notwithstanding provocations which might have excused any outbreak, kept himself clear of all envy, hatred, and malice, nor dealt otherwise than fairly and justly with the unfairness and injustice which was showered upon him; while, to the end of his days, he was ready to listen with patience and respect to the most insignificant of reasonable objectors. and with respect to that theory of the origin of the forms of life peopling our globe, with which darwin's name is bound up as closely as that of newton with the theory of gravitation, nothing seems to be further from the mind of the present generation than any attempt to smother it with ridicule or to crush it by vehemence of denunciation. "the struggle for existence," and "natural selection," have become household words and every-day conceptions. the reality and the importance of the natural processes on which darwin founds his deductions are no more doubted than those of growth and multiplication; and, whether the full potency attributed to them is admitted or not, no one doubts their vast and far-reaching significance. wherever the biological sciences are studied, the 'origin of species' lights the paths of the investigator; wherever they are taught it permeates the course of instruction. nor has the influence of darwinian ideas been less profound, beyond the realms of biology. the oldest of all philosophies, that of evolution, was bound hand and foot and cast into utter darkness during the millennium of theological scholasticism. but darwin poured new life-blood into the ancient frame; the bonds burst, and the revivified thought of ancient greece has proved itself to be a more adequate expression of the universal order of things than any of the schemes which have been accepted by the credulity and welcomed by the superstition of seventy later generations of men. to any one who studies the signs of the times, the emergence of the philosophy of evolution, in the attitude of claimant to the throne of the world of thought, from the limbo of hated and, as many hoped, forgotten things, is the most portentous event of the nineteenth century. but the most effective weapons of the modern champions of evolution were fabricated by darwin; and the 'origin of species' has enlisted a formidable body of combatants, trained in the severe school of physical science, whose ears might have long remained deaf to the speculations of a priori philosophers. i do not think any candid or instructed person will deny the truth of that which has just been asserted. he may hate the very name of evolution, and may deny its pretensions as vehemently as a jacobite denied those of george the second. but there it is--not only as solidly seated as the hanoverian dynasty, but happily independent of parliamentary sanction--and the dullest antagonists have come to see that they have to deal with an adversary whose bones are to be broken by no amount of bad words. even the theologians have almost ceased to pit the plain meaning of genesis against the no less plain meaning of nature. their more candid, or more cautious, representatives have given up dealing with evolution as if it were a damnable heresy, and have taken refuge in one of two courses. either they deny that genesis was meant to teach scientific truth, and thus save the veracity of the record at the expense of its authority; or they expend their energies in devising the cruel ingenuities of the reconciler, and torture texts in the vain hope of making them confess the creed of science. but when the peine forte et dure is over, the antique sincerity of the venerable sufferer always reasserts itself. genesis is honest to the core, and professes to be no more than it is, a repository of venerable traditions of unknown origin, claiming no scientific authority and possessing none. as my pen finishes these passages, i can but be amused to think what a terrible hubbub would have been made (in truth was made) about any similar expressions of opinion a quarter of a century ago. in fact, the contrast between the present condition of public opinion upon the darwinian question; between the estimation in which darwin's views are now held in the scientific world; between the acquiescence, or at least quiescence, of the theologians of the self-respecting order at the present day and the outburst of antagonism on all sides in 1858-9, when the new theory respecting the origin of species first became known to the older generation to which i belong, is so startling that, except for documentary evidence, i should be sometimes inclined to think my memories dreams. i have a great respect for the younger generation myself (they can write our lives, and ravel out all our follies, if they choose to take the trouble, by and by), and i should be glad to be assured that the feeling is reciprocal; but i am afraid that the story of our dealings with darwin may prove a great hindrance to that veneration for our wisdom which i should like them to display. we have not even the excuse that, thirty years ago, mr. darwin was an obscure novice, who had no claims on our attention. on the contrary, his remarkable zoological and geological investigations had long given him an assured position among the most eminent and original investigators of the day; while his charming 'voyage of a naturalist' had justly earned him a wide-spread reputation among the general public. i doubt if there was any man then living who had a better right to expect that anything he might choose to say on such a question as the origin of species would be listened to with profound attention, and discussed with respect; and there was certainly no man whose personal character should have afforded a better safeguard against attacks, instinct with malignity and spiced with shameless impertinences. yet such was the portion of one of the kindest and truest men that it was ever my good fortune to know; and years had to pass away before misrepresentation, ridicule, and denunciation, ceased to be the most notable constituents of the majority of the multitudinous criticisms of his work which poured from the press. i am loth to rake any of these ancient scandals from their well-deserved oblivion; but i must make good a statement which may seem overcharged to the present generation, and there is no piece justificative more apt for the purpose, or more worthy of such dishonour, than the article in the 'quarterly review' for july, 1860. (i was not aware when i wrote these passages that the authorship of the article had been publicly acknowledged. confession unaccompanied by penitence, however, affords no ground for mitigation of judgment; and the kindliness with which mr. darwin speaks of his assailant, bishop wilberforce (vol. ii.), is so striking an exemplification of his singular gentleness and modesty, that it rather increases one's indignation against the presumption of his critic.) since lord brougham assailed dr. young, the world has seen no such specimen of the insolence of a shallow pretender to a master in science as this remarkable production, in which one of the most exact of observers, most cautious of reasoners, and most candid of expositors, of this or any other age, is held up to scorn as a "flighty" person, who endeavours "to prop up his utterly rotten fabric of guess and speculation," and whose "mode of dealing with nature" is reprobated as "utterly dishonourable to natural science." and all this high and mighty talk, which would have been indecent in one of mr. darwin's equals, proceeds from a writer whose want of intelligence, or of conscience, or of both, is so great, that, by way of an objection to mr. darwin's views, he can ask, "is it credible that all favourable varieties of turnips are tending to become men;" who is so ignorant of paleontology, that he can talk of the "flowers and fruits" of the plants of the carboniferous epoch; of comparative anatomy, that he can gravely affirm the poison apparatus of the venomous snakes to be "entirely separate from the ordinary laws of animal life, and peculiar to themselves;" of the rudiments of physiology, that he can ask, "what advantage of life could alter the shape of the corpuscles into which the blood can be evaporated?" nor does the reviewer fail to flavour this outpouring of preposterous incapacity with a little stimulation of the odium theologicum. some inkling of the history of the conflicts between astronomy, geology, and theology, leads him to keep a retreat open by the proviso that he cannot "consent to test the truth of natural science by the word of revelation;" but, for all that, he devotes pages to the exposition of his conviction that mr. darwin's theory "contradicts the revealed relation of the creation to its creator," and is "inconsistent with the fulness of his glory." if i confine my retrospect of the reception of the 'origin of species' to a twelvemonth, or thereabouts, from the time of its publication, i do not recollect anything quite so foolish and unmannerly as the 'quarterly review' article, unless, perhaps, the address of a reverend professor to the dublin geological society might enter into competition with it. but a large proportion of mr. darwin's critics had a lamentable resemblance to the 'quarterly' reviewer, in so far as they lacked either the will, or the wit, to make themselves masters of his doctrine; hardly any possessed the knowledge required to follow him through the immense range of biological and geological science which the 'origin' covered; while, too commonly, they had prejudiced the case on theological grounds, and, as seems to be inevitable when this happens, eked out lack of reason by superfluity of railing. but it will be more pleasant and more profitable to consider those criticisms, which were acknowledged by writers of scientific authority, or which bore internal evidence of the greater or less competency and, often, of the good faith, of their authors. restricting my survey to a twelvemonth, or thereabouts, after the publication of the 'origin,' i find among such critics louis agassiz ("the arguments presented by darwin in favor of a universal derivation from one primary form of all the peculiarities existing now among living beings have not made the slightest impression on my mind." "until the facts of nature are shown to have been mistaken by those who have collected them, and that they have a different meaning from that now generally assigned to them, i shall therefore consider the transmutation theory as a scientific mistake, untrue in its facts, unscientific in its method, and mischievous in its tendency."--silliman's 'journal,' july, 1860, pages 143, 154. extract from the 3rd volume of 'contributions to the natural history of the united states.'); murray, an excellent entomologist; harvey, a botanist of considerable repute; and the author of an article in the 'edinburgh review,' all strongly adverse to darwin. pictet, the distinguished and widely learned paleontogist of geneva, treats mr. darwin with a respect which forms a grateful contrast to the tone of some of the preceding writers, but consents to go with him only a very little way. ("i see no serious objections to the formation of varieties by natural selection in the existing world, and that, so far as earlier epochs are concerned, this law may be assumed to explain the origin of closely allied species, supposing for this purpose a very long period of time." "with regard to simple varieties and closely allied species, i believe that mr. darwin's theory may explain many things, and throw a great light upon numerous questions."--'sur l'origine de l'espece. par charles darwin.' 'archives des sc. de la bibliotheque universelle de geneve,' pages 242, 243, mars 1860.) on the other hand, lyell, up to that time a pillar of the anti-transmutationists (who regarded him, ever afterwards, as pallas athene may have looked at dian, after the endymion affair), declared himself a darwinian, though not without putting in a serious caveat. nevertheless, he was a tower of strength, and his courageous stand for truth as against consistency, did him infinite honour. as evolutionists, sans phrase, i do not call to mind among the biologists more than asa gray, who fought the battle splendidly in the united states; hooker, who was no less vigorous here; the present sir john lubbock and myself. wallace was far away in the malay archipelago; but, apart from his direct share in the promulgation of the theory of natural selection, no enumeration of the influences at work, at the time i am speaking of, would be complete without the mention of his powerful essay 'on the law which has regulated the introduction of new species,' which was published in 1855. on reading it afresh, i have been astonished to recollect how small was the impression it made. in france, the influence of elie de beaumont and of flourens--the former of whom is said to have "damned himself to everlasting fame" by inventing the nickname of "la science moussante" for evolutionism (one is reminded of the effect of another small academic epigram. the so-called vertebral theory of the skull is said to have been nipped in the bud in france by the whisper of an academician to his neighbour, that, in that case, one's head was a "vertebre pensante."),--to say nothing of the ill-will of other powerful members of the institut, produced for a long time the effect of a conspiracy of silence; and many years passed before the academy redeemed itself from the reproach that the name of darwin was not to be found on the list of its members. however, an accomplished writer, out of the range of academical influences, m. laugel, gave an excellent and appreciative notice of the 'origin' in the 'revue des deux mondes.' germany took time to consider; bronn produced a slightly bowdlerized translation of the 'origin'; and 'kladderadatsch' cut his jokes upon the ape origin of man; but i do not call to mind that any scientific notability declared himself publicly in 1860. (however, the man who stands next to darwin in his influence on modern biologists, k.e. von baer, wrote to me, in august 1860, expressing his general assent to evolutionist views. his phrase, "j'ai enonce les memes idees...que m. darwin" (volume ii.) is shown by his subsequent writings to mean no more than this.) none of us dreamed that, in the course of a few years, the strength (and perhaps i may add the weakness) of "darwinismus" would have its most extensive and most brilliant illustrations in the land of learning. if a foreigner may presume to speculate on the cause of this curious interval of silence, i fancy it was that one moiety of the german biologists were orthodox at any price, and the other moiety as distinctly heterodox. the latter were evolutionists, a priori, already, and they must have felt the disgust natural to deductive philosophers at being offered an inductive and experimental foundation for a conviction which they had reached by a shorter cut. it is undoubtedly trying to learn that, though your conclusions may be all right, your reasons for them are all wrong, or, at any rate, insufficient. on the whole, then, the supporters of mr. darwin's views in 1860 were numerically extremely insignificant. there is not the slightest doubt that, if a general council of the church scientific had been held at that time, we should have been condemned by an overwhelming majority. and there is as little doubt that, if such a council gathered now, the decree would be of an exactly contrary nature. it would indicate a lack of sense, as well as of modesty, to ascribe to the men of that generation less capacity or less honesty than their successors possess. what, then, are the causes which led instructed and fair-judging men of that day to arrive at a judgment so different from that which seems just and fair to those who follow them? that is really one of the most interesting of all questions connected with the history of science, and i shall try to answer it. i am afraid that in order to do so i must run the risk of appearing egotistical. however, if i tell my own story it is only because i know it better than that of other people. i think i must have read the 'vestiges' before i left england in 1846; but, if i did, the book made very little impression upon me, and i was not brought into serious contact with the 'species' question until after 1850. at that time, i had long done with the pentateuchal cosmogony, which had been impressed upon my childish understanding as divine truth, with all the authority of parents and instructors, and from which it had cost me many a struggle to get free. but my mind was unbiassed in respect of any doctrine which presented itself, if it professed to be based on purely philosophical and scientific reasoning. it seemed to me then (as it does now) that "creation," in the ordinary sense of the word, is perfectly conceivable. i find no difficulty in imagining that, at some former period, this universe was not in existence; and that it made its appearance in six days (or instantaneously, if that is preferred), in consequence of the volition of some pre-existent being. then, as now, the so-called a priori arguments against theism; and, given a deity, against the possibility of creative acts, appeared to me to be devoid of reasonable foundation. i had not then, and i have not now, the smallest a priori objection to raise to the account of the creation of animals and plants given in 'paradise lost,' in which milton so vividly embodies the natural sense of genesis. far be it from me to say that it is untrue because it is impossible. i confine myself to what must be regarded as a modest and reasonable request for some particle of evidence that the existing species of animals and plants did originate in that way, as a condition of my belief in a statement which appears to me to be highly improbable. and, by way of being perfectly fair, i had exactly the same answer to give to the evolutionists of 1851-8. within the ranks of the biologists, at that time, i met with nobody, except dr. grant, of university college, who had a word to say for evolution--and his advocacy was not calculated to advance the cause. outside these ranks, the only person known to me whose knowledge and capacity compelled respect, and who was, at the same time, a thorough-going evolutionist, was mr. herbert spencer, whose acquaintance i made, i think, in 1852, and then entered into the bonds of a friendship which, i am happy to think, has known no interruption. many and prolonged were the battles we fought on this topic. but even my friend's rare dialectic skill and copiousness of apt illustration could not drive me from my agnostic position. i took my stand upon two grounds: firstly, that up to that time, the evidence in favour of transmutation was wholly insufficient; and secondly, that no suggestion respecting the causes of the transmutation assumed, which had been made, was in any way adequate to explain the phenomena. looking back at the state of knowledge at that time, i really do not see that any other conclusion was justifiable. in those days i had never even heard of treviranus' 'biologie.' however, i had studied lamarck attentively and i had read the 'vestiges' with due care; but neither of them afforded me any good ground for changing my negative and critical attitude. as for the 'vestiges,' i confess that the book simply irritated me by the prodigious ignorance and thoroughly unscientific habit of mind manifested by the writer. if it had any influence on me at all, it set me against evolution; and the only review i ever have qualms of conscience about, on the ground of needless savagery, is one i wrote on the 'vestiges' while under that influence. with respect to the 'philosophie zoologique,' it is no reproach to lamarck to say that the discussion of the species question in that work, whatever might be said for it in 1809, was miserably below the level of the knowledge of half a century later. in that interval of time the elucidation of the structure of the lower animals and plants had given rise to wholly new conceptions of their relations; histology and embryology, in the modern sense, had been created; physiology had been reconstituted; the facts of distribution, geological and geographical, had been prodigiously multiplied and reduced to order. to any biologist whose studies had carried him beyond mere species-mongering in 1850, one-half of lamarck's arguments were obsolete and the other half erroneous, or defective, in virtue of omitting to deal with the various classes of evidence which had been brought to light since his time. moreover his one suggestion as to the cause of the gradual modification of species--effort excited by change of conditions--was, on the face of it, inapplicable to the whole vegetable world. i do not think that any impartial judge who reads the 'philosophie zoologique' now, and who afterwards takes up lyell's trenchant and effectual criticism (published as far back as 1830), will be disposed to allot to lamarck a much higher place in the establishment of biological evolution than that which bacon assigns to himself in relation to physical science generally,--buccinator tantum. (erasmus darwin first promulgated lamarck's fundamental conceptions, and, with greater logical consistency, he had applied them to plants. but the advocates of his claims have failed to show that he, in any respect, anticipated the central idea of the 'origin of species.') but, by a curious irony of fate, the same influence which led me to put as little faith in modern speculations on this subject, as in the venerable traditions recorded in the first two chapters of genesis, was perhaps more potent than any other in keeping alive a sort of pious conviction that evolution, after all, would turn out true. i have recently read afresh the first edition of the 'principles of geology'; and when i consider that this remarkable book had been nearly thirty years in everybody's hands, and that it brings home to any reader of ordinary intelligence a great principle and a great fact--the principle, that the past must be explained by the present, unless good cause be shown to the contrary; and the fact, that, so far as our knowledge of the past history of life on our globe goes, no such cause can be shown (the same principle and the same fact guide the result from all sound historical investigation. grote's 'history of greece' is a product of the same intellectual movement as lyell's 'principles.')--i cannot but believe that lyell, for others, as for myself, was the chief agent for smoothing the road for darwin. for consistent uniformitarianism postulates evolution as much in the organic as in the inorganic world. the origin of a new species by other than ordinary agencies would be a vastly greater "catastrophe" than any of those which lyell successfully eliminated from sober geological speculation. in fact, no one was better aware of this than lyell himself. (lyell, with perfect right, claims this position for himself. he speaks of having "advocated a law of continuity even in the organic world, so far as possible without adopting lamarck's theory of transmutation"... "but while i taught that as often as certain forms of animals and plants disappeared, for reasons quite intelligible to us, others took their place by virtue of a causation which was beyond our comprehension; it remained for darwin to accumulate proof that there is no break between the incoming and the outgoing species, that they are the work of evolution, and not of special creation... "i had certainly prepared the way in this country, in six editions of my work before the 'vestiges of creation' appeared in 1842 [1844], for the reception of darwin's gradual and insensible evolution of species."--'life and letters,' letter to haeckel, volume ii. page 436. november 23, 1868.) if one reads any of the earlier editions of the 'principles' carefully (especially by the light of the interesting series of letters recently published by sir charles lyell's biographer), it is easy to see that, with all his energetic opposition to lamarck, on the one hand, and to the ideal quasi-progressionism of agassiz, on the other, lyell, in his own mind, was strongly disposed to account for the origination of all past and present species of living things by natural causes. but he would have liked, at the same time, to keep the name of creation for a natural process which he imagined to be incomprehensible. in a letter addressed to mantell (dated march 2, 1827), lyell speaks of having just read lamarck; he expresses his delight at lamarck's theories, and his personal freedom from any objection based on theological grounds. and though he is evidently alarmed at the pithecoid origin of man involved in lamarck's doctrine, he observes:-"but, after all, what changes species may really undergo! how impossible will it be to distinguish and lay down a line, beyond which some of the so-called extinct species have never passed into recent ones." again, the following remarkable passage occurs in the postscript of a letter addressed to sir john herschel in 1836:-"in regard to the origination of new species, i am very glad to find that you think it probable that it may be carried on through the intervention of intermediate causes. i left this rather to be inferred, not thinking it worth while to offend a certain class of persons by embodying in words what would only be a speculation." (in the same sense, see the letter to whewell, march 7, 1837, volume ii., page 5:-"in regard to this last subject [the changes from one set of animal and vegetable species to another]...you remember what herschel said in his letter to me. if i had stated as plainly as he has done the possibility of the introduction or origination of fresh species being a natural, in contradistinction to a miraculous process, i should have raised a host of prejudices against me, which are unfortunately opposed at every step to any philosopher who attempts to address the public on these mysterious subjects." see also letter to sedgwick, january 12, 1838 ii. page 35.) he goes on to refer to the criticisms which have been directed against him on the ground that, by leaving species to be originated by miracle, he is inconsistent with his own doctrine of uniformitarianism; and he leaves it to be understood that he had not replied, on the ground of his general objection to controversy. lyell's contemporaries were not without some inkling of his esoteric doctrine. whewell's 'history of the inductive sciences,' whatever its philosophical value, is always worth reading and always interesting, if under no other aspect than that of an evidence of the speculative limits within which a highly-placed divine might, at that time, safely range at will. in the course of his discussion of uniformitarianism, the encyclopaedic master of trinity observes:-"mr. lyell, indeed, has spoken of an hypothesis that 'the successive creation of species may constitute a regular part of the economy of nature,' but he has nowhere, i think, so described this process as to make it appear in what department of science we are to place the hypothesis. are these new species created by the production, at long intervals, of an offspring different in species from the parents? or are the species so created produced without parents? are they gradually evolved from some embryo substance? or do they suddenly start from the ground, as in the creation of the poet?... "some selection of one of these forms of the hypothesis, rather than the others, with evidence for the selection, is requisite to entitle us to place it among the known causes of change, which in this chapter we are considering. the bare conviction that a creation of species has taken place, whether once or many times, so long as it is unconnected with our organical sciences, is a tenet of natural theology rather than of physical philosophy." (whewell's 'history,' volume iii. page 639-640 (edition 2, 1847.)) the earlier part of this criticism appears perfectly just and appropriate; but, from the concluding paragraph, whewell evidently imagines that by "creation" lyell means a preternatural intervention of the deity; whereas the letter to herschel shows that, in his own mind, lyell meant natural causation; and i see no reason to doubt (the following passages in lyell's letters appear to me decisive on this point:-to darwin, october 3, 1859 (ii, 325), on first reading the 'origin.' "i have long seen most clearly that if any concession is made, all that you claim in your concluding pages will follow. "it is this which has made me so long hesitate, always feeling that the case of man and his races, and of other animals, and that of plants, is one and the same, and that if a vera causa be admitted for one instant, [instead] of a purely unknown and imaginary one, such as the word 'creation,' all the consequences must follow." to darwin, march 15, 1863 (volume ii. page 365). "i remember that it was the conclusion he [lamarck] came to about man that fortified me thirty years ago against the great impression which his arguments at first made on my mind, all the greater because constant prevost, a pupil of cuvier's forty years ago, told me his conviction 'that cuvier thought species not real, but that science could not advance without assuming that they were so.'" to hooker, march 9, 1863 (volume ii. page 361), in reference to darwin's feeling about the 'antiquity of man.' "he [darwin] seems much disappointed that i do not go farther with him, or do not speak out more. i can only say that i have spoken out to the full extent of my present convictions, and even beyond my state of feeling as to man's unbroken descent from the brutes, and i find i am half converting not a few who were in arms against darwin, and are even now against huxley." he speaks of having had to abandon "old and long cherished ideas, which constituted the charm to me of the theoretical part of the science in my earlier day, when i believed with pascal in the theory, as hallam terms it, of 'the arch-angel ruined.'" see the same sentiment in the letter to darwin, march 11, 1863, page 363:-"i think the old 'creation' is almost as much required as ever, but of course it takes a new form if lamarck's views improved by yours are adopted.") that, if sir charles could have avoided the inevitable corollary of the pithecoid origin of man--for which, to the end of his life, he entertained a profound antipathy--he would have advocated the efficiency of causes now in operation to bring about the condition of the organic world, as stoutly as he championed that doctrine in reference to inorganic nature. the fact is, that a discerning eye might have seen that some form or other of the doctrine of transmutation was inevitable, from the time when the truth enunciated by william smith that successive strata are characterised by different kinds of fossil remains, became a firmly established law of nature. no one has set forth the speculative consequences of this generalisation better than the historian of the 'inductive sciences':-"but the study of geology opens to us the spectacle of many groups of species which have, in the course of the earth's history, succeeded each other at vast intervals of time; one set of animals and plants disappearing, as it would seem, from the face of our planet, and others, which did not before exist, becoming the only occupants of the globe. and the dilemma then presents itself to us anew:--either we must accept the doctrine of the transmutation of species, and must suppose that the organized species of one geological epoch were transmuted into those of another by some long-continued agency of natural causes; or else, we must believe in many successive acts of creation and extinction of species, out of the common course of nature; acts which, therefore, we may properly call miraculous." (whewell's 'history of the inductive sciences.' edition ii., 1847, volume iii. pages 624-625. see for the author's verdict, pages 638-39.) dr. whewell decides in favour of the latter conclusion. and if any one had plied him with the four questions which he puts to lyell in the passage already cited, all that can be said now is that he would certainly have rejected the first. but would he really have had the courage to say that a rhinoceros tichorhinus, for instance, "was produced without parents;" or was "evolved from some embryo substance;" or that it suddenly started from the ground like milton's lion "pawing to get free his hinder parts." i permit myself to doubt whether even the master of trinity's well-tried courage--physical, intellectual, and moral--would have been equal to this feat. no doubt the sudden concurrence of half-a-ton of inorganic molecules into a live rhinoceros is conceivable, and therefore may be possible. but does such an event lie sufficiently within the bounds of probability to justify the belief in its occurrence on the strength of any attainable, or, indeed, imaginable, evidence? in view of the assertion (often repeated in the early days of the opposition to darwin) that he had added nothing to lamarck, it is very interesting to observe that the possibility of a fifth alternative, in addition to the four he has stated, has not dawned upon dr. whewell's mind. the suggestion that new species may result from the selective action of external conditions upon the variations from their specific type which individuals present--and which we call "spontaneous," because we are ignorant of their causation--is as wholly unknown to the historian of scientific ideas as it was to biological specialists before 1858. but that suggestion is the central idea of the 'origin of species,' and contains the quintessence of darwinism. thus, looking back into the past, it seems to me that my own position of critical expectancy was just and reasonable, and must have been taken up, on the same grounds, by many other persons. if agassiz told me that the forms of life which had successively tenanted the globe were the incarnations of successive thoughts of the deity; and that he had wiped out one set of these embodiments by an appalling geological catastrophe as soon as his ideas took a more advanced shape, i found myself not only unable to admit the accuracy of the deductions from the facts of paleontology, upon which this astounding hypothesis was founded, but i had to confess my want of any means of testing the correctness of his explanation of them. and besides that, i could by no means see what the explanation explained. neither did it help me to be told by an eminent anatomist that species had succeeded one another in time, in virtue of "a continuously operative creational law." that seemed to me to be no more than saying that species had succeeded one another, in the form of a vote-catching resolution, with "law" to please the man of science, and "creational" to draw the orthodox. so i took refuge in that "thatige skepsis" which goethe has so well defined; and, reversing the apostolic precept to be all things to all men, i usually defended the tenability of the received doctrines, when i had to do with the transmutationists; and stood up for the possibility of transmutation among the orthodox--thereby, no doubt, increasing an already current, but quite undeserved, reputation for needless combativeness. i remember, in the course of my first interview with mr. darwin, expressing my belief in the sharpness of the lines of demarcation between natural groups and in the absence of transitional forms, with all the confidence of youth and imperfect knowledge. i was not aware, at that time, that he had then been many years brooding over the species-question; and the humorous smile which accompanied his gentle answer, that such was not altogether his view, long haunted and puzzled me. but it would seem that four or five years' hard work had enabled me to understand what it meant; for lyell ('life and letters,' volume ii. page 212.), writing to sir charles bunbury (under date of april 30, 1856), says:-"when huxley, hooker, and wollaston were at darwin's last week they (all four of them) ran a tilt against species--further, i believe, than they are prepared to go." i recollect nothing of this beyond the fact of meeting mr. wollaston; and except for sir charles' distinct assurance as to "all four," i should have thought my "outrecuidance" was probably a counterblast to wollaston's conservatism. with regard to hooker, he was already, like voltaire's habbakuk, "capable du tout" in the way of advocating evolution. as i have already said, i imagine that most of those of my contemporaries who thought seriously about the matter, were very much in my own state of mind--inclined to say to both mosaists and evolutionists, "a plague on both your houses!" and disposed to turn aside from an interminable and apparently fruitless discussion, to labour in the fertile fields of ascertainable fact. and i may, therefore, further suppose that the publication of the darwin and wallace papers in 1858, and still more that of the 'origin' in 1859, had the effect upon them of the flash of light, which to a man who has lost himself in a dark night, suddenly reveals a road which, whether it takes him straight home or not, certainly goes his way. that which we were looking for, and could not find, was a hypothesis respecting the origin of known organic forms, which assumed the operation of no causes but such as could be proved to be actually at work. we wanted, not to pin our faith to that or any other speculation, but to get hold of clear and definite conceptions which could be brought face to face with facts and have their validity tested. the 'origin' provided us with the working hypothesis we sought. moreover, it did the immense service of freeing us for ever from the dilemma--refuse to accept the creation hypothesis, and what have you to propose that can be accepted by any cautious reasoner? in 1857, i had no answer ready, and i do not think that any one else had. a year later, we reproached ourselves with dullness for being perplexed by such an inquiry. my reflection, when i first made myself master of the central idea of the 'origin,' was, "how extremely stupid not to have thought of that!" i suppose that columbus' companions said much the same when he made the egg stand on end. the facts of variability, of the struggle for existence, of adaptation to conditions, were notorious enough; but none of us had suspected that the road to the heart of the species problem lay through them, until darwin and wallace dispelled the darkness, and the beacon-fire of the 'origin' guided the benighted. whether the particular shape which the doctrine of evolution, as applied to the organic world, took in darwin's hands, would prove to be final or not, was, to me, a matter of indifference. in my earliest criticisms of the 'origin' i ventured to point out that its logical foundation was insecure so long as experiments in selective breeding had not produced varieties which were more or less infertile; and that insecurity remains up to the present time. but, with any and every critical doubt which my sceptical ingenuity could suggest, the darwinian hypothesis remained incomparably more probable than the creation hypothesis. and if we had none of us been able to discern the paramount significance of some of the most patent and notorious of natural facts, until they were, so to speak, thrust under our noses, what force remained in the dilemma--creation or nothing? it was obvious that, hereafter, the probability would be immensely greater, that the links of natural causation were hidden from our purblind eyes, than that natural causation should be incompetent to produce all the phenomena of nature. the only rational course for those who had no other object than the attainment of truth, was to accept "darwinism" as a working hypothesis, and see what could be made of it. either it would prove its capacity to elucidate the facts of organic life, or it would break down under the strain. this was surely the dictate of common sense; and, for once, common sense carried the day. the result has been that complete volte-face of the whole scientific world, which must seem so surprising to the present generation. i do not mean to say that all the leaders of biological science have avowed themselves darwinians; but i do not think that there is a single zoologist, or botanist, or palaeontologist, among the multitude of active workers of this generation, who is other than an evolutionist, profoundly influenced by darwin's views. whatever may be the ultimate fate of the particular theory put forth by darwin, i venture to affirm that, so far as my knowledge goes, all the ingenuity and all the learning of hostile critics have not enabled them to adduce a solitary fact, of which it can be said, this is irreconcilable with the darwinian theory. in the prodigious variety and complexity of organic nature, there are multitudes of phenomena which are not deducible from any generalisations we have yet reached. but the same may be said of every other class of natural objects. i believe that astronomers cannot yet get the moon's motions into perfect accordance with the theory of gravitation. it would be inappropriate, even if it were possible, to discuss the difficulties and unresolved problems which have hitherto met the evolutionist, and which will probably continue to puzzle him for generations to come, in the course of this brief history of the reception of mr. darwin's great work. but there are two or three objections of a more general character, based, or supposed to be based, upon philosophical and theological foundations, which were loudly expressed in the early days of the darwinian controversy, and which, though they have been answered over and over again, crop up now and then to the present day. the most singular of these, perhaps immortal, fallacies, which live on, tithonus-like, when sense and force have long deserted them, is that which charges mr. darwin with having attempted to reinstate the old pagan goddess, chance. it is said that he supposes variations to come about "by chance," and that the fittest survive the "chances" of the struggle for existence, and thus "chance" is substituted for providential design. it is not a little wonderful that such an accusation as this should be brought against a writer who has, over and over again, warned his readers that when he uses the word "spontaneous," he merely means that he is ignorant of the cause of that which is so termed; and whose whole theory crumbles to pieces if the uniformity and regularity of natural causation for illimitable past ages is denied. but probably the best answer to those who talk of darwinism meaning the reign of "chance," is to ask them what they themselves understand by "chance"? do they believe that anything in this universe happens without reason or without a cause? do they really conceive that any event has no cause, and could not have been predicted by any one who had a sufficient insight into the order of nature? if they do, it is they who are the inheritors of antique superstition and ignorance, and whose minds have never been illumined by a ray of scientific thought. the one act of faith in the convert to science, is the confession of the universality of order and of the absolute validity in all times and under all circumstances, of the law of causation. this confession is an act of faith, because, by the nature of the case, the truth of such propositions is not susceptible of proof. but such faith is not blind, but reasonable; because it is invariably confirmed by experience, and constitutes the sole trustworthy foundation for all action. if one of these people, in whom the chance-worship of our remoter ancestors thus strangely survives, should be within reach of the sea when a heavy gale is blowing, let him betake himself to the shore and watch the scene. let him note the infinite variety of form and size of the tossing waves out at sea; or of the curves of their foam-crested breakers, as they dash against the rocks; let him listen to the roar and scream of the shingle as it is cast up and torn down the beach; or look at the flakes of foam as they drive hither and thither before the wind; or note the play of colours, which answers a gleam of sunshine as it falls upon the myriad bubbles. surely here, if anywhere, he will say that chance is supreme, and bend the knee as one who has entered the very penetralia of his divinity. but the man of science knows that here, as everywhere, perfect order is manifested; that there is not a curve of the waves, not a note in the howling chorus, not a rainbow-glint on a bubble, which is other than a necessary consequence of the ascertained laws of nature; and that with a sufficient knowledge of the conditions, competent physico-mathematical skill could account for, and indeed predict, every one of these "chance" events. a second very common objection to mr. darwin's views was (and is), that they abolish teleology, and eviscerate the argument from design. it is nearly twenty years since i ventured to offer some remarks on this subject, and as my arguments have as yet received no refutation, i hope i may be excused for reproducing them. i observed, "that the doctrine of evolution is the most formidable opponent of all the commoner and coarser forms of teleology. but perhaps the most remarkable service to the philosophy of biology rendered by mr. darwin is the reconciliation of teleology and morphology, and the explanation of the facts of both, which his views offer. the teleology which supposes that the eye, such as we see it in man, or one of the higher vertebrata, was made with the precise structure it exhibits, for the purpose of enabling the animal which possesses it to see, has undoubtedly received its death-blow. nevertheless, it is necessary to remember that there is a wider teleology which is not touched by the doctrine of evolution, but is actually based upon the fundamental proposition of evolution. this proposition is that the whole world, living and not living, is the result of the mutual interaction, according to definite laws, of the forces (i should now like to substitute the word powers for "forces.") possessed by the molecules of which the primitive nebulosity of the universe was composed. if this be true, it is no less certain that the existing world lay potentially in the cosmic vapour, and that a sufficient intelligence could, from a knowledge of the properties of the molecules of that vapour, have predicted, say the state of the fauna of britain in 1869, with as much certainty as one can say what will happen to the vapour of the breath on a cold winter's day... ...the teleological and the mechanical views of nature are not, necessarily, mutually exclusive. on the contrary, the more purely a mechanist the speculator is, the more firmly does he assume a primordial molecular arrangement of which all the phenomena of the universe are the consequences, and the more completely is he thereby at the mercy of the teleologist, who can always defy him to disprove that this primordial molecular arrangement was not intended to evolve the phenomena of the universe." (the "genealogy of animals" ('the academy,' 1869), reprinted in 'critiques and addresses.') the acute champion of teleology, paley, saw no difficulty in admitting that the "production of things" may be the result of trains of mechanical dispositions fixed beforehand by intelligent appointment and kept in action by a power at the centre ('natural theology,' chapter xxiii.), that is to say, he proleptically accepted the modern doctrine of evolution; and his successors might do well to follow their leader, or at any rate to attend to his weighty reasonings, before rushing into an antagonism which has no reasonable foundation. having got rid of the belief in chance and the disbelief in design, as in no sense appurtenances of evolution, the third libel upon that doctrine, that it is anti-theistic, might perhaps be left to shift for itself. but the persistence with which many people refuse to draw the plainest consequences from the propositions they profess to accept, renders it advisable to remark that the doctrine of evolution is neither anti-theistic nor theistic. it simply has no more to do with theism than the first book of euclid has. it is quite certain that a normal fresh-laid egg contains neither cock nor hen; and it is also as certain as any proposition in physics or morals, that if such an egg is kept under proper conditions for three weeks, a cock or hen chicken will be found in it. it is also quite certain that if the shell were transparent we should be able to watch the formation of the young fowl, day by day, by a process of evolution, from a microscopic cellular germ to its full size and complication of structure. therefore evolution, in the strictest sense, is actually going on in this and analogous millions and millions of instances, wherever living creatures exist. therefore, to borrow an argument from butler, as that which now happens must be consistent with the attributes of the deity, if such a being exists, evolution must be consistent with those attributes. and, if so, the evolution of the universe, which is neither more nor less explicable than that of a chicken, must also be consistent with them. the doctrine of evolution, therefore, does not even come into contact with theism, considered as a philosophical doctrine. that with which it does collide, and with which it is absolutely inconsistent, is the conception of creation, which theological speculators have based upon the history narrated in the opening of the book of genesis. there is a great deal of talk and not a little lamentation about the so-called religious difficulties which physical science has created. in theological science, as a matter of fact, it has created none. not a solitary problem presents itself to the philosophical theist, at the present day, which has not existed from the time that philosophers began to think out the logical grounds and the logical consequences of theism. all the real or imaginary perplexities which flow from the conception of the universe as a determinate mechanism, are equally involved in the assumption of an eternal, omnipotent and omniscient deity. the theological equivalent of the scientific conception of order is providence; and the doctrine of determinism follows as surely from the attributes of foreknowledge assumed by the theologian, as from the universality of natural causation assumed by the man of science. the angels in 'paradise lost' would have found the task of enlightening adam upon the mysteries of "fate, foreknowledge, and free-will," not a whit more difficult, if their pupil had been educated in a "real-schule" and trained in every laboratory of a modern university. in respect of the great problems of philosophy, the post-darwinian generation is, in one sense, exactly where the prae-darwinian generations were. they remain insoluble. but the present generation has the advantage of being better provided with the means of freeing itself from the tyranny of certain sham solutions. the known is finite, the unknown infinite; intellectually we stand on an islet in the midst of an illimitable ocean of inexplicability. our business in every generation is to reclaim a little more land, to add something to the extent and the solidity of our possessions. and even a cursory glance at the history of the biological sciences during the last quarter of a century is sufficient to justify the assertion, that the most potent instrument for the extension of the realm of natural knowledge which has come into men's hands, since the publication of newton's 'principia,' is darwin's 'origin of species.' it was badly received by the generation to which it was first addressed, and the outpouring of angry nonsense to which it gave rise is sad to think upon. but the present generation will probably behave just as badly if another darwin should arise, and inflict upon them that which the generality of mankind most hate--the necessity of revising their convictions. let them, then, be charitable to us ancients; and if they behave no better than the men of my day to some new benefactor, let them recollect that, after all, our wrath did not come to much, and vented itself chiefly in the bad language of sanctimonious scolds. let them as speedily perform a strategic right-about-face, and follow the truth wherever it leads. the opponents of the new truth will discover, as those of darwin are doing, that, after all, theories do not alter facts, and that the universe remains unaffected even though texts crumble. or, it may be, that, as history repeats itself, their happy ingenuity will also discover that the new wine is exactly of the same vintage as the old, and that (rightly viewed) the old bottles prove to have been expressly made for holding it. the origin of species [1] by thomas h. huxley mr. darwin's long-standing and well-earned scientific eminence probably renders him indifferent to that social notoriety which passes by the name of success; but if the calm spirit of the philosopher have not yet wholly superseded the ambition and the vanity of the carnal man within him, he must be well satisfied with the results of his venture in publishing the 'origin of species'. overflowing the narrow bounds of purely scientific circles, the "species question" divides with italy and the volunteers the attention of general society. everybody has read mr. darwin's book, or, at least, has given an opinion upon its merits or demerits; pietists, whether lay or ecclesiastic, decry it with the mild railing which sounds so charitable; bigots denounce it with ignorant invective; old ladies of both sexes consider it a decidedly dangerous book, and even savants, who have no better mud to throw, quote antiquated writers to show that its author is no better than an ape himself; while every philosophical thinker hails it as a veritable whitworth gun in the armoury of liberalism; and all competent naturalists and physiologists, whatever their opinions as to the ultimate fate of the doctrines put forth, acknowledge that the work in which they are embodied is a solid contribution to knowledge and inaugurates a new epoch in natural history. nor has the discussion of the subject been restrained within the limits of conversation. when the public is eager and interested, reviewers must minister to its wants; and the genuine 'litterateur' is too much in the habit of acquiring his knowledge from the book he judges--as the abyssinian is said to provide himself with steaks from the ox which carries him--to be withheld from criticism of a profound scientific work by the mere want of the requisite preliminary scientific acquirement; while, on the other hand, the men of science who wish well to the new views, no less than those who dispute their validity, have naturally sought opportunities of expressing their opinions. hence it is not surprising that almost all the critical journals have noticed mr. darwin's work at greater or less length; and so many disquisitions, of every degree of excellence, from the poor product of ignorance, too often stimulated by prejudice, to the fair and thoughtful essay of the candid student of nature, have appeared, that it seems an almost hopeless task to attempt to say anything new upon the question. but it may be doubted if the knowledge and acumen of prejudged scientific opponents, or the subtlety of orthodox special pleaders, have yet exerted their full force in mystifying the real issues of the great controversy which has been set afoot, and whose end is hardly likely to be seen by this generation; so that, at this eleventh hour, and even failing anything new, it may be useful to state afresh that which is true, and to put the fundamental positions advocated by mr. darwin in such a form that they may be grasped by those whose special studies lie in other directions. and the adoption of this course may be the more advisable, because, notwithstanding its great deserts, and indeed partly on account of them, the 'origin of species' is by no means an easy book to read--if by reading is implied the full comprehension of an author's meaning. we do not speak jestingly in saying that it is mr. darwin's misfortune to know more about the question he has taken up than any man living. personally and practically exercised in zoology, in minute anatomy, in geology; a student of geographical distribution, not on maps and in museums only, but by long voyages and laborious collection; having largely advanced each of these branches of science, and having spent many years in gathering and sifting materials for his present work, the store of accurately registered facts upon which the author of the 'origin of species' is able to draw at will is prodigious. but this very superabundance of matter must have been embarrassing to a writer who, for the present, can only put forward an abstract of his views; and thence it arises, perhaps, that notwithstanding the clearness of the style, those who attempt fairly to digest the book find much of it a sort of intellectual pemmican--a mass of facts crushed and pounded into shape, rather than held together by the ordinary medium of an obvious logical bond; due attention will, without doubt, discover this bond, but it is often hard to find. again, from sheer want of room, much has to be taken for granted which might readily enough be proved; and hence, while the adept, who can supply the missing links in the evidence from his own knowledge, discovers fresh proof of the singular thoroughness with which all difficulties have been considered and all unjustifiable suppositions avoided, at every reperusal of mr. darwin's pregnant paragraphs, the novice in biology is apt to complain of the frequency of what he fancies is gratuitous assumption. thus while it may be doubted if, for some years, any one is likely to be competent to pronounce judgment on all the issues raised by mr. darwin, there is assuredly abundant room for him, who, assuming the humbler, though perhaps as useful, office of an interpreter between the 'origin of species' and the public, contents himself with endeavouring to point out the nature of the problems which it discusses; to distinguish between the ascertained facts and the theoretical views which it contains; and finally, to show the extent to which the explanation it offers satisfies the requirements of scientific logic. at any rate, it is this office which we purpose to undertake in the following pages. it may be safely assumed that our readers have a general conception of the nature of the objects to which the word "species" is applied; but it has, perhaps, occurred to a few, even to those who are naturalists 'ex professo', to reflect, that, as commonly employed, the term has a double sense and denotes two very different orders of relations. when we call a group of animals, or of plants, a species, we may imply thereby, either that all these animals or plants have some common peculiarity of form or structure; or, we may mean that they possess some common functional character. that part of biological science which deals with form and structure is called morphology--that which concerns itself with function, physiology--so that we may conveniently speak of these two senses, or aspects, of "species"--the one as morphological, the other as physiological. regarded from the former point of view, a species is nothing more than a kind of animal or plant, which is distinctly definable from all others, by certain constant, and not merely sexual, morphological peculiarities. thus horses form a species, because the group of animals to which that name is applied is distinguished from all others in the world by the following constantly associated characters. they have--1, a vertebral column; 2, mammae; 3, a placental embryo; 4, four legs; 5, a single well-developed toe in each foot provided with a hoof; 6, a bushy tail; and 7, callosities on the inner sides of both the fore and the hind legs. the asses, again, form a distinct species, because, with the same characters, as far as the fifth in the above list, all asses have tufted tails, and have callosities only on the inner side of the fore-legs. if animals were discovered having the general characters of the horse, but sometimes with callosities only on the fore-legs, and more or less tufted tails; or animals having the general characters of the ass, but with more or less bushy tails, and sometimes with callosities on both pairs of legs, besides being intermediate in other respects--the two species would have to be merged into one. they could no longer be regarded as morphologically distinct species, for they would not be distinctly definable one from the other. however bare and simple this definition of species may appear to be, we confidently appeal to all practical naturalists, whether zoologists, botanists, or palaeontologists, to say if, in the vast majority of cases, they know, or mean to affirm anything more of the group of animals or plants they so denominate than what has just been stated. even the most decided advocates of the received doctrines respecting species admit this. "i apprehend," says professor owen [2], "that few naturalists nowadays, in describing and proposing a name for what they call 'a new species,' use that term to signify what was meant by it twenty or thirty years ago; that is, an originally distinct creation, maintaining its primitive distinction by obstructive generative peculiarities. the proposer of the new species now intends to state no more than he actually knows; as, for example, that the differences on which he founds the specific character are constant in individuals of both sexes, so far as observation has reached; and that they are not due to domestication or to artificially superinduced external circumstances, or to any outward influence within his cognizance; that the species is wild, or is such as it appears by nature." if we consider, in fact, that by far the largest proportion of recorded existing species are known only by the study of their skins, or bones, or other lifeless exuvia; that we are acquainted with none, or next to none, of their physiological peculiarities, beyond those which can be deduced from their structure, or are open to cursory observation; and that we cannot hope to learn more of any of those extinct forms of life which now constitute no inconsiderable proportion of the known flora and fauna of the world: it is obvious that the definitions of these species can be only of a purely structural, or morphological, character. it is probable that naturalists would have avoided much confusion of ideas if they had more frequently borne the necessary limitations of our knowledge in mind. but while it may safely be admitted that we are acquainted with only the morphological characters of the vast majority of species--the functional or physiological, peculiarities of a few have been carefully investigated, and the result of that study forms a large and most interesting portion of the physiology of reproduction. the student of nature wonders the more and is astonished the less, the more conversant he becomes with her operations; but of all the perennial miracles she offers to his inspection, perhaps the most worthy of admiration is the development of a plant or of an animal from its embryo. examine the recently laid egg of some common animal, such as a salamander or newt. it is a minute spheroid in which the best microscope will reveal nothing but a structureless sac, enclosing a glairy fluid, holding granules in suspension. but strange possibilities lie dormant in that semi-fluid globule. let a moderate supply of warmth reach its watery cradle, and the plastic matter undergoes changes so rapid, yet so steady and purposelike in their succession, that one can only compare them to those operated by a skilled modeller upon a formless lump of clay. as with an invisible trowel, the mass is divided and subdivided into smaller and smaller portions, until it is reduced to an aggregation of granules not too large to build withal the finest fabrics of the nascent organism. and, then, it is as if a delicate finger traced out the line to be occupied by the spinal column, and moulded the contour of the body; pinching up the head at one end, the tail at the other, and fashioning flank and limb into due salamandrine proportions, in so artistic a way, that, after watching the process hour by hour, one is almost involuntarily possessed by the notion, that some more subtle aid to vision than an achromatic, would show the hidden artist, with his plan before him, striving with skilful manipulation to perfect his work. as life advances, and the young amphibian ranges the waters, the terror of his insect contemporaries, not only are the nutritious particles supplied by its prey, by the addition of which to its frame, growth takes place, laid down, each in its proper spot, and in such due proportion to the rest, as to reproduce the form, the colour, and the size, characteristic of the parental stock; but even the wonderful powers of reproducing lost parts possessed by these animals are controlled by the same governing tendency. cut off the legs, the tail, the jaws, separately or all together, and, as spallanzani showed long ago, these parts not only grow again, but the redintegrated limb is formed on the same type as those which were lost. the new jaw, or leg, is a newt's, and never by any accident more like that of a frog. what is true of the newt is true of every animal and of every plant; the acorn tends to build itself up again into a woodland giant such as that from whose twig it fell; the spore of the humblest lichen reproduces the green or brown incrustation which gave it birth; and at the other end of the scale of life, the child that resembled neither the paternal nor the maternal side of the house would be regarded as a kind of monster. so that the one end to which, in all living beings, the formative impulse is tending--the one scheme which the archaeus of the old speculators strives to carry out, seems to be to mould the offspring into the likeness of the parent. it is the first great law of reproduction, that the offspring tends to resemble its parent or parents, more closely than anything else. science will some day show us how this law is a necessary consequence of the more general laws which govern matter; but, for the present, more can hardly be said than that it appears to be in harmony with them. we know that the phenomena of vitality are not something apart from other physical phenomena, but one with them; and matter and force are the two names of the one artist who fashions the living as well as the lifeless. hence living bodies should obey the same great laws as other matter--nor, throughout nature, is there a law of wider application than this, that a body impelled by two forces takes the direction of their resultant. but living bodies may be regarded as nothing but extremely complex bundles of forces held in a mass of matter, as the complex forces of a magnet are held in the steel by its coercive force; and, since the differences of sex are comparatively slight, or, in other words, the sum of the forces in each has a very similar tendency, their resultant, the offspring, may reasonably be expected to deviate but little from a course parallel to either, or to both. represent the reason of the law to ourselves by what physical metaphor or analogy we will, however, the great matter is to apprehend its existence and the importance of the consequences deducible from it. for things which are like to the same are like to one another; and if; in a great series of generations, every offspring is like its parent, it follows that all the offspring and all the parents must be like one another; and that, given an original parental stock, with the opportunity of undisturbed multiplication, the law in question necessitates the production, in course of time, of an indefinitely large group, the whole of whose members are at once very similar and are blood relations, having descended from the same parent, or pair of parents. the proof that all the members of any given group of animals, or plants, had thus descended, would be ordinarily considered sufficient to entitle them to the rank of physiological species, for most physiologists consider species to be definable as "the offspring of a single primitive stock." but though it is quite true that all those groups we call species 'may', according to the known laws of reproduction, have descended from a single stock, and though it is very likely they really have done so, yet this conclusion rests on deduction and can hardly hope to establish itself upon a basis of observation. and the primitiveness of the supposed single stock, which, after all, is the essential part of the matter, is not only a hypothesis, but one which has not a shadow of foundation, if by "primitive" he meant "independent of any other living being." a scientific definition, of which an unwarrantable hypothesis forms an essential part, carries its condemnation within itself; but, even supposing such a definition were, in form, tenable, the physiologist who should attempt to apply it in nature would soon find himself involved in great, if not inextricable, difficulties. as we have said, it is indubitable that offspring 'tend' to resemble the parental organism, but it is equally true that the similarity attained never amounts to identity, either in form or in structure. there is always a certain amount of deviation, not only from the precise characters of a single parent, but when, as in most animals and many plants, the sexes are lodged in distinct individuals, from an exact mean between the two parents. and indeed, on general principles, this slight deviation seems as intelligible as the general similarity, if we reflect how complex the co-operating "bundles of forces" are, and how improbable it is that, in any case, their true resultant shall coincide with any mean between the more obvious characters of the two parents. whatever be its cause, however, the co-existence of this tendency to minor variation with the tendency to general similarity, is of vast importance in its bearing on the question of the origin of species. as a general rule, the extent to which an offspring differs from its parent is slight enough; but, occasionally, the amount of difference is much more strongly marked, and then the divergent offspring receives the name of a variety. multitudes, of what there is every reason to believe are such varieties, are known, but the origin of very few has been accurately recorded, and of these we will select two as more especially illustrative of the main features of variation. the first of them is that of the "ancon," or "otter" sheep, of which a careful account is given by colonel david humphreys, f.r.s., in a letter to sir joseph banks, published in the philosophical transactions for 1813. it appears that one seth wright, the proprietor of a farm on the banks of the charles river, in massachusetts, possessed a flock of fifteen ewes and a ram of the ordinary kind. in the year 1791, one of the ewes presented her owner with a male lamb, differing, for no assignable reason, from its parents by a proportionally long body and short bandy legs, whence it was unable to emulate its relatives in those sportive leaps over the neighbours' fences, in which they were in the habit of indulging, much to the good farmer's vexation. the second case is that detailed by a no less unexceptionable authority than reaumur, in his 'art de faire eclore les poulets'. a maltese couple, named kelleia, whose hands and feet were constructed upon the ordinary human model, had born to them a son, gratio, who possessed six perfectly movable fingers on each hand, and six toes, not quite so well formed, on each foot. no cause could be assigned for the appearance of this unusual variety of the human species. two circumstances are well worthy of remark in both these cases. in each, the variety appears to have arisen in full force, and, as it were, 'per saltum'; a wide and definite difference appearing, at once, between the ancon ram and the ordinary sheep; between the six-fingered and six-toed gratio kelleia and ordinary men. in neither case is it possible to point out any obvious reason for the appearance of the variety. doubtless there were determining causes for these as for all other phenomena; but they do not appear, and we can be tolerably certain that what are ordinarily understood as changes in physical conditions, as in climate, in food, or the like, did not take place and had nothing to do with the matter. it was no case of what is commonly called adaptation to circumstances; but, to use a conveniently erroneous phrase, the variations arose spontaneously. the fruitless search after final causes leads their pursuers a long way; but even those hardy teleologists, who are ready to break through all the laws of physics in chase of their favourite will-o'-the-wisp, may be puzzled to discover what purpose could be attained by the stunted legs of seth wright's ram or the hexadactyle members of gratio kelleia. varieties then arise we know not why; and it is more than probable that the majority of varieties have arisen in this "spontaneous" manner, though we are, of course, far from denying that they may be traced, in some cases, to distinct external influences; which are assuredly competent to alter the character of the tegumentary covering, to change colour, to increase or diminish the size of muscles, to modify constitution, and, among plants, to give rise to the metamorphosis of stamens into petals, and so forth. but however they may have arisen, what especially interests us at present is, to remark that, once in existence, varieties obey the fundamental law of reproduction that like tends to produce like; and their offspring exemplify it by tending to exhibit the same deviation from the parental stock as themselves. indeed, there seems to be, in many instances, a pre-potent influence about a newly-arisen variety which gives it what one may call an unfair advantage over the normal descendants from the same stock. this is strikingly exemplified by the case of gratio kelleia, who married a woman with the ordinary pentadactyle extremities, and had by her four children, salvator, george, andre, and marie. of these children salvator, the eldest boy, had six fingers and six toes, like his father; the second and third, also boys, had five fingers and five toes, like their mother, though the hands and feet of george were slightly deformed. the last, a girl, had five fingers and five toes, but the thumbs were slightly deformed. the variety thus reproduced itself purely in the eldest, while the normal type reproduced itself purely in the third, and almost purely in the second and last: so that it would seem, at first, as if the normal type were more powerful than the variety. but all these children grew up and intermarried with normal wives and husband, and then, note what took place: salvator had four children, three of whom exhibited the hexadactyle members of their grandfather and father, while the youngest had the pentadactyle limbs of the mother and grandmother; so that here, notwithstanding a double pentadactyle dilution of the blood, the hexadactyle variety had the best of it. the same pre-potency of the variety was still more markedly exemplified in the progeny of two of the other children, marie and george. marie (whose thumbs only were deformed) gave birth to a boy with six toes, and three other normally formed children; but george, who was not quite so pure a pentadactyle, begot, first, two girls, each of whom had six fingers and toes; then a girl with six fingers on each hand and six toes on the right foot, but only five toes on the left; and lastly, a boy with only five fingers and toes. in these instances, therefore, the variety, as it were, leaped over one generation to reproduce itself in full force in the next. finally, the purely pentadactyle andre was the father of many children, not one of whom departed from the normal parental type. if a variation which approaches the nature of a monstrosity can strive thus forcibly to reproduce itself, it is not wonderful that less aberrant modifications should tend to be preserved even more strongly; and the history of the ancon sheep is, in this respect, particularly instructive. with the "'cuteness" characteristic of their nation, the neighbours of the massachusetts farmer imagined it would be an excellent thing if all his sheep were imbued with the stay-at-home tendencies enforced by nature upon the newly-arrived ram; and they advised wright to kill the old patriarch of his fold, and install the ancon ram in his place. the result justified their sagacious anticipations, and coincided very nearly with what occurred to the progeny of gratio kelleia. the young lambs were almost always either pure ancons, or pure ordinary sheep. [3] but when sufficient ancon sheep were obtained to interbreed with one another, it was found that the offspring was always pure ancon. colonel humphreys, in fact, states that he was acquainted with only "one questionable case of a contrary nature." here, then, is a remarkable and well-established instance, not only of a very distinct race being established 'per saltum', but of that race breeding "true" at once, and showing no mixed forms, even when crossed with another breed. by taking care to select ancons of both sexes, for breeding from, it thus became easy to establish an extremely well-marked race; so peculiar that, even when herded with other sheep, it was noted that the ancons kept together. and there is every reason to believe that the existence of this breed might have been indefinitely protracted; but the introduction of the merino sheep, which were not only very superior to the ancons in wool and meat, but quite as quiet and orderly, led to the complete neglect of the new breed, so that, in 1813, colonel humphreys found it difficult to obtain the specimen, whose skeleton was presented to sir joseph banks. we believe that, for many years, no remnant of it has existed in the united states. gratio kelleia was not the progenitor of a race of six-fingered men, as seth wright's ram became a nation of ancon sheep, though the tendency of the variety to perpetuate itself appears to have been fully as strong in the one case as in the other. and the reason of the difference is not far to seek. seth wright took care not to weaken the ancon blood by matching his ancon ewes with any but males of the same variety, while gratio kelleia's sons were too far removed from the patriarchal times to intermarry with their sisters; and his grandchildren seem not to have been attracted by their six-fingered cousins. in other words, in the one example a race was produced, because, for several generations, care was taken to 'select' both parents of the breeding stock from animals exhibiting a tendency to vary in the same condition; while, in the other, no race was evolved, because no such selection was exercised. a race is a propagated variety; and as, by the laws of reproduction, offspring tend to assume the parental forms, they will be more likely to propagate a variation exhibited by both parents than that possessed by only one. there is no organ of the body of an animal which may not, and does not, occasionally, vary more or less from the normal type; and there is no variation which may not be transmitted and which, if selectively transmitted, may not become the foundation of a race. this great truth, sometimes forgotten by philosophers, has long been familiar to practical agriculturists and breeders; and upon it rest all the methods of improving the breeds of domestic animals, which, for the last century, have been followed with so much success in england. colour, form, size, texture of hair or wool, proportions of various parts, strength or weakness of constitution, tendency to fatten or to remain lean, to give much or little milk, speed, strength, temper, intelligence, special instincts; there is not one of these characters whose transmission is not an every-day occurrence within the experience of cattle-breeders, stock-farmers, horse-dealers, and dog and poultry fanciers. nay, it is only the other day that an eminent physiologist, dr. brown-sequard, communicated to the royal society his discovery that epilepsy, artificially produced in guinea-pigs, by a means which he has discovered, is transmitted to their offspring. but a race, once produced, is no more a fixed and immutable entity than the stock whence it sprang; variations arise among its members, and as these variations are transmitted like any others, new races may be developed out of the pre-existing one 'ad infinitum', or, at least, within any limit at present determined. given sufficient time and sufficiently careful selection, and the multitude of races which may arise from a common stock is as astonishing as are the extreme structural differences which they may present. a remarkable example of this is to be found in the rock-pigeon, which dr. darwin has, in our opinion, satisfactorily demonstrated to be the progenitor of all our domestic pigeons, of which there are certainly more than a hundred well-marked races. the most noteworthy of these races are, the four great stocks known to the "fancy" as tumblers, pouters, carriers, and fantails; birds which not only differ most singularly in size, colour, and habits, but in the form of the beak and of the skull: in the proportions of the beak to the skull; in the number of tail-feathers; in the absolute and relative size of the feet; in the presence or absence of the uropygial gland; in the number of vertebrae in the back; in short, in precisely those characters in which the genera and species of birds differ from one another. and it is most remarkable and instructive to observe, that none of these races can be shown to have been originated by the action of changes in what are commonly called external circumstances, upon the wild rock-pigeon. on the contrary, from time immemorial, pigeon-fanciers have had essentially similar methods of treating their pets, which have been housed, fed, protected and cared for in much the same way in all pigeonries. in fact, there is no case better adapted than that of the pigeons to refute the doctrine which one sees put forth on high authority, that "no other characters than those founded on the development of bone for the attachment of muscles" are capable of variation. in precise contradiction of this hasty assertion, mr. darwin's researches prove that the skeleton of the wings in domestic pigeons has hardly varied at all from that of the wild type; while, on the other hand, it is in exactly those respects, such as the relative length of the beak and skull, the number of the vertebrae, and the number of the tail-feathers, in which muscular exertion can have no important influence, that the utmost amount of variation has taken place. we have said that the following out of the properties exhibited by physiological species would lead us into difficulties, and at this point they begin to be obvious; for if, as the result of spontaneous variation and of selective breeding, the progeny of a common stock may become separated into groups distinguished from one another by constant, not sexual, morphological characters, it is clear that the physiological definition of species is likely to clash with the morphological definition. no one would hesitate to describe the pouter and the tumbler as distinct species, if they were found fossil, or if their skins and skeletons were imported, as those of exotic wild birds commonly are--and without doubt, if considered alone, they are good and distinct morphological species. on the other hand, they are not physiological species, for they are descended from a common stock, the rock-pigeon. under these circumstances, as it is admitted on all sides that races occur in nature, how are we to know whether any apparently distinct animals are really of different physiological species, or not, seeing that the amount of morphological difference is no safe guide? is there any test of a physiological species? the usual answer of physiologists is in the affirmative. it is said that such a test is to be found in the phenomena of hybridization--in the results of crossing races, as compared with the results of crossing species. so far as the evidence goes at present, individuals, of what are certainly known to be mere races produced by selection, however distinct they may appear to be, not only breed freely together, but the offspring of such crossed races are only perfectly fertile with one another. thus, the spaniel and the greyhound, the dray-horse and the arab, the pouter and the tumbler, breed together with perfect freedom, and their mongrels, if matched with other mongrels of the same kind, are equally fertile. on the other hand, there can be no doubt that the individuals of many natural species are either absolutely infertile if crossed with individuals of other species, or, if they give rise to hybrid offspring, the hybrids so produced are infertile when paired together. the horse and the ass, for instance, if so crossed, give rise to the mule, and there is no certain evidence of offspring ever having been produced by a male and female mule. the unions of the rock-pigeon and the ring-pigeon appear to be equally barren of result. here, then, says the physiologist, we have a means of distinguishing any two true species from any two varieties. if a male and a female, selected from each group, produce offspring, and that offspring is fertile with others produced in the same way, the groups are races and not species. if, on the other hand, no result ensues, or if the offspring are infertile with others produced in the same way, they are true physiological species. the test would be an admirable one, if, in the first place, it were always practicable to apply it, and if, in the second, it always yielded results susceptible of a definite interpretation. unfortunately, in the great majority of cases, this touchstone for species is wholly inapplicable. the constitution of many wild animals is so altered by confinement that they will not breed even with their own females, so that the negative results obtained from crosses are of no value; and the antipathy of wild animals of the same species for one another, or even of wild and tame members of the same species, is ordinarily so great, that it is hopeless to look for such unions in nature. the hermaphrodism of most plants, the difficulty in the way of insuring the absence of their own, or the proper working of other pollen, are obstacles of no less magnitude in applying the test to them. and, in both animals and plants, is superadded the further difficulty, that experiments must be continued over a long time for the purpose of ascertaining the fertility of the mongrel or hybrid progeny, as well as of the first crosses from which they spring. not only do these great practical difficulties lie in the way of applying the hybridization test, but even when this oracle can be questioned, its replies are sometimes as doubtful as those of delphi. for example, cases are cited by mr. darwin, of plants which are more fertile with the pollen of another species than with their own; and there are others, such as certain 'fuci', whose male element will fertilize the ovule of a plant of distinct species, while the males of the latter species are ineffective with the females of the first. so that, in the last-named instance, a physiologist, who should cross the two species in one way, would decide that they were true species; while another, who should cross them in the reverse way, would, with equal justice, according to the rule, pronounce them to be mere races. several plants, which there is great reason to believe are mere varieties, are almost sterile when crossed; while both animals and plants, which have always been regarded by naturalists as of distinct species, turn out, when the test is applied, to be perfectly fertile. again, the sterility or fertility of crosses seems to bear no relation to the structural resemblances or differences of the members of any two groups. mr. darwin has discussed this question with singular ability and circumspection, and his conclusions are summed up as follows, at page 276 of his work:-"first crosses between forms sufficiently distinct to be ranked as species, and their hybrids, are very generally, but not universally, sterile. the sterility is of all degrees, and is often so slight that the two most careful experimentalists who have ever lived have come to diametrically opposite conclusions in ranking forms by this test. the sterility is innately variable in individuals of the same species, and is eminently susceptible of favourable and unfavourable conditions. the degree of sterility does not strictly follow systematic affinity, but is governed by several curious and complex laws. it is generally different and sometimes widely different, in reciprocal crosses between the same two species. it is not always equal in degree in a first cross, and in the hybrid produced from this cross. "in the same manner as in grafting trees, the capacity of one species or variety to take on another is incidental on generally unknown differences in their vegetative systems; so in crossing, the greater or less facility of one species to unite with another is incidental on unknown differences in their reproductive systems. there is no more reason to think that species have been specially endowed with various degrees of sterility to prevent them crossing and breeding in nature, than to think that trees have been specially endowed with various and somewhat analogous degrees of difficulty in being grafted together, in order to prevent them becoming inarched in our forests. "the sterility of first crosses between pure species, which have their reproductive systems perfect, seems to depend on several circumstances; in some cases largely on the early death of the embryo. the sterility of hybrids which have their reproductive systems imperfect, and which have had this system and their whole organization disturbed by being compounded of two distinct species, seems closely allied to that sterility which so frequently affects pure species when their natural conditions of life have been disturbed. this view is supported by a parallelism of another kind: namely, that the crossing of forms, only slightly different, is favourable to the vigour and fertility of the offspring; and that slight changes in the conditions of life are apparently favourable to the vigour and fertility of all organic beings. it is not surprising that the degree of difficulty in uniting two species, and the degree of sterility of their hybrid offspring, should generally correspond, though due to distinct causes; for both depend on the amount of difference of some kind between the species which are crossed. nor is it surprising that the facility of effecting a first cross, the fertility of hybrids produced from it, and the capacity of being grafted together--though this latter capacity evidently depends on widely different circumstances--should all run to a certain extent parallel with the systematic affinity of the forms which are subjected to experiment; for systematic affinity attempts to express all kinds of resemblance between all species. "first crosses between forms known to be varieties, or sufficiently alike to be considered as varieties, and their mongrel offspring, are very generally, but not quite universally, fertile. nor is this nearly general and perfect fertility surprising, when we remember how liable we are to argue in a circle with respect to varieties in a state of nature; and when we remember that the greater number of varieties have been produced under domestication by the selection of mere external differences, and not of differences in the reproductive system. in all other respects, excluding fertility, there is a close general resemblance between hybrids and mongrels."--pp. 276-8. we fully agree with the general tenor of this weighty passage; but forcible as are these arguments, and little as the value of fertility or infertility as a test of species may be, it must not be forgotten that the really important fact, so far as the inquiry into the origin of species goes, is, that there are such things in nature as groups of animals and of plants, whose members are incapable of fertile union with those of other groups; and that there are such things as hybrids, which are absolutely sterile when crossed with other hybrids. for, if such phenomena as these were exhibited by only two of those assemblages of living objects, to which the name of species (whether it be used in its physiological or in its morphological sense) is given, it would have to be accounted for by any theory of the origin of species, and every theory which could not account for it would be, so far, imperfect. up to this point, we have been dealing with matters of fact, and the statements which we have laid before the reader would, to the best of our knowledge, be admitted to contain a fair exposition of what is at present known respecting the essential properties of species, by all who have studied the question. and whatever may be his theoretical views, no naturalist will probably be disposed to demur to the following summary of that exposition:-living beings, whether animals or plants, are divisible into multitudes of distinctly definable kinds, which are morphological species. they are also divisible into groups of individuals, which breed freely together, tending to reproduce their like, and are physiological species. normally resembling their parents, the offspring of members of these species are still liable to vary; and the variation may be perpetuated by selection, as a race, which race, in many cases, presents all the characteristics of a morphological species. but it is not as yet proved that a race ever exhibits, when crossed with another race of the same species, those phenomena of hybridization which are exhibited by many species when crossed with other species. on the other hand, not only is it not proved that all species give rise to hybrids infertile 'inter se', but there is much reason to believe that, in crossing, species exhibit every gradation from perfect sterility to perfect fertility. such are the most essential characteristics of species. even were man not one of them--a member of the same system and subject to the same laws--the question of their origin, their causal connexion, that is, with the other phenomena of the universe, must have attracted his attention, as soon as his intelligence had raised itself above the level of his daily wants. indeed history relates that such was the case, and has embalmed for us the speculations upon the origin of living beings, which were among the earliest products of the dawning intellectual activity of man. in those early days positive knowledge was not to be had, but the craving after it needed, at all hazards, to be satisfied, and according to the country, or the turn of thought, of the speculator, the suggestion that all living things arose from the mud of the nile, from a primeval egg, or from some more anthropomorphic agency, afforded a sufficient resting-place for his curiosity. the myths of paganism are as dead as osiris or zeus, and the man who should revive them, in opposition to the knowledge of our time, would be justly laughed to scorn; but the coeval imaginations current among the rude inhabitants of palestine, recorded by writers whose very name and age are admitted by every scholar to be unknown, have unfortunately not yet shared their fate, but, even at this day, are regarded by nine-tenths of the civilized world as the authoritative standard of fact and the criterion of the justice of scientific conclusions, in all that relates to the origin of things, and, among them, of species. in this nineteenth century, as at the dawn of modern physical science, the cosmogony of the semi-barbarous hebrew is the incubus of the philosopher and the opprobrium of the orthodox. who shall number the patient and earnest seekers after truth, from the days of galileo until now, whose lives have been embittered and their good name blasted by the mistaken zeal of bibliolaters? who shall count the host of weaker men whose sense of truth has been destroyed in the effort to harmonize impossibilities--whose life has been wasted in the attempt to force the generous new wine of science into the old bottles of judaism, compelled by the outcry of the same strong party? it is true that if philosophers have suffered, their cause has been amply avenged. extinguished theologians lie about the cradle of every science as the strangled snakes beside that of hercules; and history records that whenever science and orthodoxy have been fairly opposed, the latter has been forced to retire from the lists, bleeding and crushed if not annihilated; scotched, if not slain. but orthodoxy is the bourbon of the world of thought. it learns not, neither can it forget; and though, at present, bewildered and afraid to move, it is as willing as ever to insist that the first chapter of genesis contains the beginning and the end of sound science; and to visit, with such petty thunderbolts as its half-paralysed hands can hurl, those who refuse to degrade nature to the level of primitive judaism. philosophers, on the other hand, have no such aggressive tendencies. with eyes fixed on the noble goal to which "per aspera et ardua" they tend, they may, now and then, be stirred to momentary wrath by the unnecessary obstacles with which the ignorant, or the malicious, encumber, if they cannot bar, the difficult path; but why should their souls be deeply vexed? the majesty of fact is on their side, and the elemental forces of nature are working for them. not a star comes to the meridian at its calculated time but testifies to the justice of their methods--their beliefs are "one with falling rain and with the growing corn." by doubt they are established, and open inquiry is their bosom friend. such men have no fear of traditions however venerable, and no respect for them when they become mischievous and obstructive; but they have better than mere antiquarian business in hand, and if dogmas, which ought to be fossil but are not, are not forced upon their notice, they are too happy to treat them as non-existent. the hypotheses respecting the origin of species which profess to stand upon a scientific basis, and, as such, alone demand serious attention, are of two kinds. the one, the "special creation" hypothesis, presumes every species to have originated from one or more stocks, these not being the result of the modification of any other form of living matter--or arising by natural agencies--but being produced, as such, by a supernatural creative act. the other, the so-called "transmutation" hypothesis, considers that all existing species are the result of the modification of pre-existing species, and those of their predecessors, by agencies similar to those which at the present day produce varieties and races, and therefore in an altogether natural way; and it is a probable, though not a necessary consequence of this hypothesis, that all living beings have arisen from a single stock. with respect to the origin of this primitive stock, or stocks, the doctrine of the origin of species is obviously not necessarily concerned. the transmutation hypothesis, for example, is perfectly consistent either with the conception of a special creation of the primitive germ, or with the supposition of its having arisen, as a modification of inorganic matter, by natural causes. the doctrine of special creation owes its existence very largely to the supposed necessity of making science accord with the hebrew cosmogony; but it is curious to observe that, as the doctrine is at present maintained by men of science, it is as hopelessly inconsistent with the hebrew view as any other hypothesis. if there be any result which has come more clearly out of geological investigation than another, it is, that the vast series of extinct animals and plants is not divisible, as it was once supposed to be, into distinct groups, separated by sharply-marked boundaries. there are no great gulfs between epochs and formations--no successive periods marked by the appearance of plants, of water animals, and of land animals, 'en masse'. every year adds to the list of links between what the older geologists supposed to be widely separated epochs: witness the crags linking the drift with older tertiaries; the maestricht beds linking the tertiaries with the chalk; the st. cassian beds exhibiting an abundant fauna of mixed mesozoic and palaeozoic types, in rocks of an epoch once supposed to be eminently poor in life; witness, lastly, the incessant disputes as to whether a given stratum shall be reckoned devonian or carboniferous, silurian or devonian, cambrian or silurian. this truth is further illustrated in a most interesting manner by the impartial and highly competent testimony of m. pictet, from whose calculations of what percentage of the genera of animals, existing in any formation, lived during the preceding formation, it results that in no case is the proportion less than 'one-third', or 33 per cent. it is the triassic formation, or the commencement of the mesozoic epoch, which has received the smallest inheritance from preceding ages. the other formations not uncommonly exhibit 60, 80, or even 94 per cent. of genera in common with those whose remains are imbedded in their predecessor. not only is this true, but the subdivisions of each formation exhibit new species characteristic of, and found only in, them; and, in many cases, as in the lias for example, the separate beds of these subdivisions are distinguished by well-marked and peculiar forms of life. a section, a hundred feet thick, will exhibit, at different heights, a dozen species of ammonite, none of which passes beyond its particular zone of limestone, or clay, into the zone below it or into that above it; so that those who adopt the doctrine of special creation must be prepared to admit, that at intervals of time, corresponding with the thickness of these beds, the creator thought fit to interfere with the natural course of events for the purpose of making a new ammonite. it is not easy to transplant oneself into the frame of mind of those who can accept such a conclusion as this, on any evidence short of absolute demonstration; and it is difficult to see what is to be gained by so doing, since, as we have said, it is obvious that such a view of the origin of living beings is utterly opposed to the hebrew cosmogony. deserving no aid from the powerful arm of bibliolatry, then, does the received form of the hypothesis of special creation derive any support from science or sound logic? assuredly not much. the arguments brought forward in its favour all take one form: if species were not supernaturally created, we cannot understand the facts 'x' or 'y', or 'z'; we cannot understand the structure of animals or plants, unless we suppose they were contrived for special ends; we cannot understand the structure of the eye, except by supposing it to have been made to see with; we cannot understand instincts, unless we suppose animals to have been miraculously endowed with them. as a question of dialectics, it must be admitted that this sort of reasoning is not very formidable to those who are not to be frightened by consequences. it is an 'argumentum ad ignorantiam'--take this explanation or be ignorant. but suppose we prefer to admit our ignorance rather than adopt a hypothesis at variance with all the teachings of nature? or, suppose for a moment we admit the explanation, and then seriously ask ourselves how much the wiser are we; what does the explanation explain? is it any more than a grandiloquent way of announcing the fact, that we really know nothing about the matter? a phenomenon is explained when it is shown to be a case of some general law of nature; but the supernatural interposition of the creator can, by the nature of the case, exemplify no law, and if species have really arisen in this way, it is absurd to attempt to discuss their origin. or, lastly, let us ask ourselves whether any amount of evidence which the nature of our faculties permits us to attain, can justify us in asserting that any phenomenon is out of the reach of natural causation. to this end it is obviously necessary that we should know all the consequences to which all possible combinations, continued through unlimited time, can give rise. if we knew these, and found none competent to originate species, we should have good ground for denying their origin by natural causation. till we know them, any hypothesis is better than one which involves us in such miserable presumption. but the hypothesis of special creation is not only a mere specious mask for our ignorance; its existence in biology marks the youth and imperfection of the science. for what is the history of every science but the history of the elimination of the notion of creative, or other interferences, with the natural order of the phenomena which are the subject-matter of that science? when astronomy was young "the morning stars sang together for joy," and the planets were guided in their courses by celestial hands. now, the harmony of the stars has resolved itself into gravitation according to the inverse squares of the distances, and the orbits of the planets are deducible from the laws of the forces which allow a schoolboy's stone to break a window. the lightning was the angel of the lord; but it has pleased providence, in these modern times, that science should make it the humble messenger of man, and we know that every flash that shimmers about the horizon on a summer's evening is determined by ascertainable conditions, and that its direction and brightness might, if our knowledge of these were great enough, have been calculated. the solvency of great mercantile companies rests on the validity of the laws which have been ascertained to govern the seeming irregularity of that human life which the moralist bewails as the most uncertain of things; plague, pestilence, and famine are admitted, by all but fools, to be the natural result of causes for the most part fully within human control, and not the unavoidable tortures inflicted by wrathful omnipotence upon his helpless handiwork. harmonious order governing eternally continuous progress--the web and woof of matter and force interweaving by slow degrees, without a broken thread, that veil which lies between us and the infinite--that universe which alone we know or can know; such is the picture which science draws of the world, and in proportion as any part of that picture is in unison with the rest, so may we feel sure that it is rightly painted. shall biology alone remain out of harmony with her sister sciences? such arguments against the hypothesis of the direct creation of species as these are plainly enough deducible from general considerations; but there are, in addition, phenomena exhibited by species themselves, and yet not so much a part of their very essence as to have required earlier mention, which are in the highest degree perplexing, if we adopt the popularly accepted hypothesis. such are the facts of distribution in space and in time; the singular phenomena brought to light by the study of development; the structural relations of species upon which our systems of classification are founded; the great doctrines of philosophical anatomy, such as that of homology, or of the community of structural plan exhibited by large groups of species differing very widely in their habits and functions. the species of animals which inhabit the sea on opposite sides of the isthmus of panama are wholly distinct [4] the animals and plants which inhabit islands are commonly distinct from those of the neighbouring mainlands, and yet have a similarity of aspect. the mammals of the latest tertiary epoch in the old and new worlds belong to the same genera, or family groups, as those which now inhabit the same great geographical area. the crocodilian reptiles which existed in the earliest secondary epoch were similar in general structure to those now living, but exhibit slight differences in their vertebrae, nasal passages, and one or two other points. the guinea-pig has teeth which are shed before it is born, and hence can never subserve the masticatory purpose for which they seem contrived, and, in like manner, the female dugong has tusks which never cut the gum. all the members of the same great group run through similar conditions in their development, and all their parts, in the adult state, are arranged according to the same plan. man is more like a gorilla than a gorilla is like a lemur. such are a few, taken at random, among the multitudes of similar facts which modern research has established; but when the student seeks for an explanation of them from the supporters of the received hypothesis of the origin of species, the reply he receives is, in substance, of oriental simplicity and brevity--"mashallah! it so pleases god!" there are different species on opposite sides of the isthmus of panama, because they were created different on the two sides. the pliocene mammals are like the existing ones, because such was the plan of creation; and we find rudimental organs and similarity of plan, because it has pleased the creator to set before himself a "divine exemplar or archetype," and to copy it in his works; and somewhat ill, those who hold this view imply, in some of them. that such verbal hocus-pocus should be received as science will one day be regarded as evidence of the low state of intelligence in the nineteenth century, just as we amuse ourselves with the phraseology about nature's abhorrence of a vacuum, wherewith torricelli's compatriots were satisfied to explain the rise of water in a pump. and be it recollected that this sort of satisfaction works not only negative but positive ill, by discouraging inquiry, and so depriving man of the usufruct of one of the most fertile fields of his great patrimony, nature. the objections to the doctrine of the origin of species by special creation which have been detailed, must have occurred, with more or less force, to the mind of every one who has seriously and independently considered the subject. it is therefore no wonder that, from time to time, this hypothesis should have been met by counter hypotheses, all as well, and some better founded than itself; and it is curious to remark that the inventors of the opposing views seem to have been led into them as much by their knowledge of geology, as by their acquaintance with biology. in fact, when the mind has once admitted the conception of the gradual production of the present physical state of our globe, by natural causes operating through long ages of time, it will be little disposed to allow that living beings have made their appearance in another way, and the speculations of de maillet and his successors are the natural complement of scilla's demonstration of the true nature of fossils. a contemporary of newton and of leibnitz, sharing therefore in the intellectual activity of the remarkable age which witnessed the birth of modern physical science, benoit de maillet spent a long life as a consular agent of the french government in various mediterranean ports. for sixteen years, in fact, he held the office of consul-general in egypt, and the wonderful phenomena offered by the valley of the nile appear to have strongly impressed his mind, to have directed his attention to all facts of a similar order which came within his observation, and to have led him to speculate on the origin of the present condition of our globe and of its inhabitants. but, with all his ardour for science, de maillet seems to have hesitated to publish views which, notwithstanding the ingenious attempts to reconcile them with the hebrew hypothesis contained in the preface to "telliamed," were hardly likely to be received with favour by his contemporaries. but a short time had elapsed since more than one of the great anatomists and physicists of the italian school had paid dearly for their endeavours to dissipate some of the prevalent errors; and their illustrious pupil, harvey, the founder of modern physiology, had not fared so well, in a country less oppressed by the benumbing influences of theology, as to tempt any man to follow his example. probably not uninfluenced by these considerations, his catholic majesty's consul-general for egypt kept his theories to himself throughout a long life, for 'telliamed,' the only scientific work which is known to have proceeded from his pen, was not printed till 1735, when its author had reached the ripe age of seventy-nine; and though de maillet lived three years longer, his book was not given to the world before 1748. even then it was anonymous to those who were not in the secret of the anagrammatic character of its title; and the preface and dedication are so worded as, in case of necessity, to give the printer a fair chance of falling back on the excuse that the work was intended for a mere 'jeu d'esprit'. the speculations of the suppositious indian sage, though quite as sound as those of many a "mosaic geology," which sells exceedingly well, have no great value if we consider them by the light of modern science. the waters are supposed to have originally covered the whole globe; to have deposited the rocky masses which compose its mountains by processes comparable to those which are now forming mud, sand, and shingle; and then to have gradually lowered their level, leaving the spoils of their animal and vegetable inhabitants embedded in the strata. as the dry land appeared, certain of the aquatic animals are supposed to have taken to it, and to have become gradually adapted to terrestrial and aerial modes of existence. but if we regard the general tenor and style of the reasoning in relation to the state of knowledge of the day, two circumstances appear very well worthy of remark. the first, that de maillet had a notion of the modifiability of living forms (though without any precise information on the subject), and how such modifiability might account for the origin of species; the second, that he very clearly apprehended the great modern geological doctrine, so strongly insisted upon by hutton, and so ably and comprehensively expounded by lyell, that we must look to existing causes for the explanation of past geological events. indeed, the following passage of the preface, in which de maillet is supposed to speak of the indian philosopher telliamed, his 'alter ego', might have been written by the most philosophical uniformitarian of the present day:-"ce qu'il y a d'etonnant, est que pour arriver a ces connoissances il semble avoir perverti l'ordre naturel, puisqu'au lieu de s'attacher d'abord a rechercher l'origine de notre globe il a commence par travailler a s'instruire de la nature. mais a l'entendre, ce renversement de l'ordre a ete pour lui l'effet d'un genie favorable qui l'a conduit pas a pas et comme par la main aux decouvertes les plus sublimes. c'est en decomposant la substance de ce globe par une anatomie exacte de toutes ses parties qu'il a premierement appris de quelles matieres il etait compose et quels arrangemens ces memes matieres observaient entre elles. ces lumieres jointes a l'esprit de comparaison toujours necessaire a quiconque entreprend de percer les voiles dont la nature aime a se cacher, ont servi de guide a notre philosophe pour parvenir a des connoissances plus interessantes. par la matiere et l'arrangement de ces compositions il pretend avoir reconnu quelle est la veritable origine de ce globe que nous habitons, comment et par qui il a ete forme."--pp. xix. xx. but de maillet was before his age, and as could hardly fail to happen to one who speculated on a zoological and botanical question before linnaeus, and on a physiological problem before haller, he fell into great errors here and there; and hence, perhaps, the general neglect of his work. robinet's speculations are rather behind, than in advance of, those of de maillet; and though linnaeus may have played with the hypothesis of transmutation, it obtained no serious support until lamarck adopted it, and advocated it with great ability in his 'philosophie zoologique.' impelled towards the hypothesis of the transmutation of species, partly by his general cosmological and geological views; partly by the conception of a graduated, though irregularly branching, scale of being, which had arisen out of his profound study of plants and of the lower forms of animal life, lamarck, whose general line of thought often closely resembles that of de maillet, made a great advance upon the crude and merely speculative manner in which that writer deals with the question of the origin of living beings, by endeavouring to find physical causes competent to effect that change of one species into another, which de maillet had only supposed to occur. and lamarck conceived that he had found in nature such causes, amply sufficient for the purpose in view. it is a physiological fact, he says, that organs are increased in size by action, atrophied by inaction; it is another physiological fact that modifications produced are transmissible to offspring. change the actions of an animal, therefore, and you will change its structure, by increasing the development of the parts newly brought into use and by the diminution of those less used; but by altering the circumstances which surround it you will alter its actions, and hence, in the long run, change of circumstance must produce change of organization. all the species of animals, therefore, are, in lamarck's view, the result of the indirect action of changes of circumstance, upon those primitive germs which he considered to have originally arisen, by spontaneous generation, within the waters of the globe. it is curious, however, that lamarck should insist so strongly [5] as he has done, that circumstances never in any degree directly modify the form or the organization of animals, but only operate by changing their wants and consequently their actions; for he thereby brings upon himself the obvious question, how, then, do plants, which cannot be said to have wants or actions, become modified? to this he replies, that they are modified by the changes in their nutritive processes, which are effected by changing circumstances; and it does not seem to have occurred to him that such changes might be as well supposed to take place among animals. when we have said that lamarck felt that mere speculation was not the way to arrive at the origin of species, but that it was necessary, in order to the establishment of any sound theory on the subject, to discover by observation or otherwise, some 'vera causa', competent to give rise to them; that he affirmed the true order of classification to coincide with the order of their development one from another; that he insisted on the necessity of allowing sufficient time, very strongly; and that all the varieties of instinct and reason were traced back by him to the same cause as that which has given rise to species, we have enumerated his chief contributions to the advance of the question. on the other hand, from his ignorance of any power in nature competent to modify the structure of animals, except the development of parts, or atrophy of them, in consequence of a change of needs, lamarck was led to attach infinitely greater weight than it deserves to this agency, and the absurdities into which he was led have met with deserved condemnation. of the struggle for existence, on which, as we shall see, mr. darwin lays such great stress, he had no conception; indeed, he doubts whether there really are such things as extinct species, unless they be such large animals as may have met their death at the hands of man; and so little does he dream of there being any other destructive causes at work, that, in discussing the possible existence of fossil shells, he asks, "pourquoi d'ailleurs seroient-ils perdues des que l'homme n'a pu operer leur destruction?" ('phil. zool.,' vol. i. p. 77.) of the influence of selection lamarck has as little notion, and he makes no use of the wonderful phenomena which are exhibited by domesticated animals, and illustrate its powers. the vast influence of cuvier was employed against the lamarckian views, and, as the untenability of some of his conclusions was easily shown, his doctrines sank under the opprobrium of scientific, as well as of theological, heterodoxy. nor have the efforts made of late years to revive them tended to re-establish their credit in the minds of sound thinkers acquainted with the facts of the case; indeed it may be doubted whether lamarck has not suffered more from his friends than from his foes. two years ago, in fact, though we venture to question if even the strongest supporters of the special creation hypothesis had not, now and then, an uneasy consciousness that all was not right, their position seemed more impregnable than ever, if not by its own inherent strength, at any rate by the obvious failure of all the attempts which had been made to carry it. on the other hand, however much the few, who thought deeply on the question of species, might be repelled by the generally received dogmas, they saw no way of escaping from them save by the adoption of suppositions so little justified by experiment or by observation as to be at least equally distasteful. the choice lay between two absurdities and a middle condition of uneasy scepticism; which last, however unpleasant and unsatisfactory, was obviously the only justifiable state of mind under the circumstances. such being the general ferment in the minds of naturalists, it is no wonder that they mustered strong in the rooms of the linnaean society, on the 1st of july of the year 1858, to hear two papers by authors living on opposite sides of the globe, working out their results independently, and yet professing to have discovered one and the same solution of all the problems connected with species. the one of these authors was an able naturalist, mr. wallace, who had been employed for some years in studying the productions of the islands of the indian archipelago, and who had forwarded a memoir embodying his views to mr. darwin, for communication to the linnaean society. on perusing the essay, mr. darwin was not a little surprised to find that it embodied some of the leading ideas of a great work which he had been preparing for twenty years, and parts of which, containing a development of the very same views, had been perused by his private friends fifteen or sixteen years before. perplexed in what manner to do full justice both to his friend and to himself, mr. darwin placed the matter in the hands of dr. hooker and sir charles lyell, by whose advice he communicated a brief abstract of his own views to the linnaean society, at the same time that mr. wallace's paper was read. of that abstract, the work on the 'origin of species' is an enlargement; but a complete statement of mr. darwin's doctrine is looked for in the large and well-illustrated work which he is said to be preparing for publication. the darwinian hypothesis has the merit of being eminently simple and comprehensible in principle, and its essential positions may be stated in a very few words: all species have been produced by the development of varieties from common stocks; by the conversion of these, first into permanent races and then into new species, by the process of 'natural selection', which process is essentially identical with that artificial selection by which man has originated the races of domestic animals--the 'struggle for existence' taking the place of man, and exerting, in the case of natural selection, that selective action which he performs in artificial selection. the evidence brought forward by mr. darwin in support of his hypothesis is of three kinds. first, he endeavours to prove that species may be originated by selection; secondly, he attempts to show that natural causes are competent to exert selection; and thirdly, he tries to prove that the most remarkable and apparently anomalous phenomena exhibited by the distribution, development, and mutual relations of species, can be shown to be deducible from the general doctrine of their origin, which he propounds, combined with the known facts of geological change; and that, even if all these phenomena are not at present explicable by it, none are necessarily inconsistent with it. there cannot be a doubt that the method of inquiry which mr. darwin has adopted is not only rigorously in accordance with the canons of scientific logic, but that it is the only adequate method. critics exclusively trained in classics or in mathematics, who have never determined a scientific fact in their lives by induction from experiment or observation, prate learnedly about mr. darwin's method, which is not inductive enough, not baconian enough, forsooth, for them. but even if practical acquaintance with the process of scientific investigation is denied them, they may learn, by the perusal of mr. mill's admirable chapter "on the deductive method," that there are multitudes of scientific inquiries in which the method of pure induction helps the investigator but a very little way. "the mode of investigation," says mr. mill, "which, from the proved inapplicability of direct methods of observation and experiment, remains to us as the main source of the knowledge we possess, or can acquire, respecting the conditions and laws of recurrence of the more complex phenomena, is called, in its most general expression, the deductive method, and consists of three operations: the first, one of direct induction; the second, of ratiocination; and the third, of verification." now, the conditions which have determined the existence of species are not only exceedingly complex, but, so far as the great majority of them are concerned, are necessarily beyond our cognizance. but what mr. darwin has attempted to do is in exact accordance with the rule laid down by mr. mill; he has endeavoured to determine certain great facts inductively, by observation and experiment; he has then reasoned from the data thus furnished; and lastly, he has tested the validity of his ratiocination by comparing his deductions with the observed facts of nature. inductively, mr. darwin endeavours to prove that species arise in a given way. deductively, he desires to show that, if they arise in that way, the facts of distribution, development, classification, etc., may be accounted for, 'i.e.' may be deduced from their mode of origin, combined with admitted changes in physical geography and climate, during an indefinite period. and this explanation, or coincidence of observed with deduced facts, is, so far as it extends, a verification of the darwinian view. there is no fault to be found with mr. darwin's method, then; but it is another question whether he has fulfilled all the conditions imposed by that method. is it satisfactorily proved, in fact, that species may be originated by selection? that there is such a thing as natural selection? that none of the phenomena exhibited by species are inconsistent with the origin of species in this way? if these questions can be answered in the affirmative, mr. darwin's view steps out of the rank of hypotheses into those of proved theories; but, so long as the evidence at present adduced falls short of enforcing that affirmation, so long, to our minds, must the new doctrine be content to remain among the former--an extremely valuable, and in the highest degree probable, doctrine, indeed the only extant hypothesis which is worth anything in a scientific point of view; but still a hypothesis, and not yet the theory of species. after much consideration, and with assuredly no bias against mr. darwin's views, it is our clear conviction that, as the evidence stands, it is not absolutely proven that a group of animals, having all the characters exhibited by species in nature, has ever been originate by selection, whether artificial or natural. groups having the morphological character of species, distinct and permanent races in fact, have been so produced over and over again; but there is no positive evidence, at present, that any group of animals has, by variation and selective breeding, given rise to another group which was, even in the least degree, infertile with the first. mr. darwin is perfectly aware of this weak point, and brings forward a multitude of ingenious and important arguments to diminish the force of the objection. we admit the value of these arguments to their fullest extent; nay, we will go so far as to express our belief that experiments, conducted by a skilful physiologist, would very probably obtain the desired production of mutually more or less infertile breeds from a common stock, in a comparatively few years; but still, as the case stands at present, this "little rift within the lute" is not to be disguised nor overlooked. in the remainder of mr. darwin's argument our own private ingenuity has not hitherto enabled us to pick holes of any great importance; and judging by what we hear and read, other adventurers in the same field do not seem to have been much more fortunate. it has been urged, for instance, that in his chapters on the struggle for existence and on natural selection, mr. darwin does not so much prove that natural selection does occur, as that it must occur; but, in fact, no other sort of demonstration is attainable. a race does not attract our attention in nature until it has, in all probability, existed for a considerable time, and then it is too late to inquire into the conditions of its origin. again, it is said that there is no real analogy between the selection which takes place under domestication, by human influence, and any operation which can be effected by nature, for man interferes intelligently. reduced to its elements, this argument implies that an effect produced with trouble by an intelligent agent must, 'a fortiori', be more troublesome, if not impossible, to an unintelligent agent. even putting aside the question whether nature, acting as she does according to definite and invariable laws, can be rightly called an unintelligent agent, such a position as this is wholly untenable. mix salt and sand, and it shall puzzle the wisest of men, with his mere natural appliances, to separate all the grains of sand from all the grains of salt; but a shower of rain will effect the same object in ten minutes. and so, while man may find it tax all his intelligence to separate any variety which arises, and to breed selectively from it, the destructive agencies incessantly at work in nature, if they find one variety to be more soluble in circumstances than the other, will inevitably, in the long run, eliminate it. a frequent and a just objection to the lamarckian hypothesis of the transmutation of species is based upon the absence of transitional forms between many species. but against the darwinian hypothesis this argument has no force. indeed, one of the most valuable and suggestive parts of mr. darwin's work is that in which he proves, that the frequent absence of transitions is a necessary consequence of his doctrine, and that the stock whence two or more species have sprung, need in no respect be intermediate between these species. if any two species have arisen from a common stock in the same way as the carrier and the pouter, say, have arisen from the rock-pigeon, then the common stock of these two species need be no more intermediate between the two than the rock-pigeon is between the carrier and pouter. clearly appreciate the force of this analogy, and all the arguments against the origin of species by selection, based on the absence of transitional forms, fall to the ground. and mr. darwin's position might, we think, have been even stronger than it is if he had not embarrassed himself with the aphorism, "natura non facit saltum," which turns up so often in his pages. we believe, as we have said above, that nature does make jumps now and then, and a recognition of the fact is of no small importance in disposing of many minor objections to the doctrine of transmutation. but we must pause. the discussion of mr. darwin's arguments in detail would lead us far beyond the limits within which we proposed, at starting, to confine this article. our object has been attained if we have given an intelligible, however brief, account of the established facts connected with species, and of the relation of the explanation of those facts offered by mr. darwin to the theoretical views held by his predecessors and his contemporaries, and, above all, to the requirements of scientific logic. we have ventured to point out that it does not, as yet, satisfy all those requirements; but we do not hesitate to assert that it is as superior to any preceding or contemporary hypothesis, in the extent of observational and experimental basis on which it rests, in its rigorously scientific method, and in its power of explaining biological phenomena, as was the hypothesis of copernicus to the speculations of ptolemy. but the planetary orbits turned out to be not quite circular after all, and, grand as was the service copernicus rendered to science, kepler and newton had to come after him. what if the orbit of darwinism should be a little too circular? what if species should offer residual phenomena, here and there, not explicable by natural selection? twenty years hence naturalists may be in a position to say whether this is, or is not, the case; but in either event they will owe the author of 'the origin of species' an immense debt of gratitude. we should leave a very wrong impression on the reader's mind if we permitted him to suppose that the value of that work depends wholly on the ultimate justification of the theoretical views which it contains. on the contrary, if they were disproved to-morrow, the book would still be the best of its kind--the most compendious statement of well-sifted facts bearing on the doctrine of species that has ever appeared. the chapters on variation, on the struggle for existence, on instinct, on hybridism, on the imperfection of the geological record, on geographical distribution, have not only no equals, but, so far as our knowledge goes, no competitors, within the range of biological literature. and viewed as a whole, we do not believe that, since the publication of von baer's researches on development, thirty years ago, any work has appeared calculated to exert so large an influence, not only on the future of biology, but in extending the domination of science over regions of thought into which she has, as yet, hardly penetrated. [footnote 1: 'the westminster review', april 1860.] [footnote 2: on the osteology of the chimpanzees and orangs: transactions of the zoological society, 1858.] [footnote 3: colonel humphreys' statements are exceedingly explicit on this point:--"when an ancon ewe is impregnated by a common ram, the increase resembles wholly either the ewe or the ram. the increase of the common ewe impregnated by an ancon ram follows entirely the one or the other, without blending any of the distinguishing and essential peculiarities of both. frequent instances have happened where common ewes have had twins by ancon rams, when one exhibited the complete marks and features of the ewe, the other of the ram. the contrast has been rendered singularly striking, when one short-legged and one long-legged lamb, produced at a birth, have been seen sucking the dam at the same time."--'philosophical transactions', 1813, pt. i. pp. 89, 90.] [footnote 4: recent investigations tend to show that this statement is not strictly accurate.--1870.] [footnote 5: see 'phil. zoologique,' vol. i. p. 222, 'et seq.'] the autobiography of charles darwin from the life and letters of charles darwin by charles darwin edited by his son francis darwin [my father's autobiographical recollections, given in the present chapter, were written for his children,--and written without any thought that they would ever be published. to many this may seem an impossibility; but those who knew my father will understand how it was not only possible, but natural. the autobiography bears the heading, 'recollections of the development of my mind and character,' and end with the following note:--"aug. 3, 1876. this sketch of my life was begun about may 28th at hopedene (mr. hensleigh wedgwood's house in surrey.), and since then i have written for nearly an hour on most afternoons." it will easily be understood that, in a narrative of a personal and intimate kind written for his wife and children, passages should occur which must here be omitted; and i have not thought it necessary to indicate where such omissions are made. it has been found necessary to make a few corrections of obvious verbal slips, but the number of such alterations has been kept down to the minimum.--f.d.] a german editor having written to me for an account of the development of my mind and character with some sketch of my autobiography, i have thought that the attempt would amuse me, and might possibly interest my children or their children. i know that it would have interested me greatly to have read even so short and dull a sketch of the mind of my grandfather, written by himself, and what he thought and did, and how he worked. i have attempted to write the following account of myself, as if i were a dead man in another world looking back at my own life. nor have i found this difficult, for life is nearly over with me. i have taken no pains about my style of writing. i was born at shrewsbury on february 12th, 1809, and my earliest recollection goes back only to when i was a few months over four years old, when we went to near abergele for sea-bathing, and i recollect some events and places there with some little distinctness. my mother died in july 1817, when i was a little over eight years old, and it is odd that i can remember hardly anything about her except her death-bed, her black velvet gown, and her curiously constructed work-table. in the spring of this same year i was sent to a day-school in shrewsbury, where i stayed a year. i have been told that i was much slower in learning than my younger sister catherine, and i believe that i was in many ways a naughty boy. by the time i went to this day-school (kept by rev. g. case, minister of the unitarian chapel in the high street. mrs. darwin was a unitarian and attended mr. case's chapel, and my father as a little boy went there with his elder sisters. but both he and his brother were christened and intended to belong to the church of england; and after his early boyhood he seems usually to have gone to church and not to mr. case's. it appears ("st. james' gazette", dec. 15, 1883) that a mural tablet has been erected to his memory in the chapel, which is now known as the 'free christian church.') my taste for natural history, and more especially for collecting, was well developed. i tried to make out the names of plants (rev. w.a. leighton, who was a schoolfellow of my father's at mr. case's school, remembers his bringing a flower to school and saying that his mother had taught him how by looking at the inside of the blossom the name of the plant could be discovered. mr. leighton goes on, "this greatly roused my attention and curiosity, and i enquired of him repeatedly how this could be done?"--but his lesson was naturally enough not transmissible.--f.d.), and collected all sorts of things, shells, seals, franks, coins, and minerals. the passion for collecting which leads a man to be a systematic naturalist, a virtuoso, or a miser, was very strong in me, and was clearly innate, as none of my sisters or brother ever had this taste. one little event during this year has fixed itself very firmly in my mind, and i hope that it has done so from my conscience having been afterwards sorely troubled by it; it is curious as showing that apparently i was interested at this early age in the variability of plants! i told another little boy (i believe it was leighton, who afterwards became a well-known lichenologist and botanist), that i could produce variously coloured polyanthuses and primroses by watering them with certain coloured fluids, which was of course a monstrous fable, and had never been tried by me. i may here also confess that as a little boy i was much given to inventing deliberate falsehoods, and this was always done for the sake of causing excitement. for instance, i once gathered much valuable fruit from my father's trees and hid it in the shrubbery, and then ran in breathless haste to spread the news that i had discovered a hoard of stolen fruit. i must have been a very simple little fellow when i first went to the school. a boy of the name of garnett took me into a cake shop one day, and bought some cakes for which he did not pay, as the shopman trusted him. when we came out i asked him why he did not pay for them, and he instantly answered, "why, do you not know that my uncle left a great sum of money to the town on condition that every tradesman should give whatever was wanted without payment to any one who wore his old hat and moved [it] in a particular manner?" and he then showed me how it was moved. he then went into another shop where he was trusted, and asked for some small article, moving his hat in the proper manner, and of course obtained it without payment. when we came out he said, "now if you like to go by yourself into that cake-shop (how well i remember its exact position) i will lend you my hat, and you can get whatever you like if you move the hat on your head properly." i gladly accepted the generous offer, and went in and asked for some cakes, moved the old hat and was walking out of the shop, when the shopman made a rush at me, so i dropped the cakes and ran for dear life, and was astonished by being greeted with shouts of laughter by my false friend garnett. i can say in my own favour that i was as a boy humane, but i owed this entirely to the instruction and example of my sisters. i doubt indeed whether humanity is a natural or innate quality. i was very fond of collecting eggs, but i never took more than a single egg out of a bird's nest, except on one single occasion, when i took all, not for their value, but from a sort of bravado. i had a strong taste for angling, and would sit for any number of hours on the bank of a river or pond watching the float; when at maer (the house of his uncle, josiah wedgwood.) i was told that i could kill the worms with salt and water, and from that day i never spitted a living worm, though at the expense probably of some loss of success. once as a very little boy whilst at the day school, or before that time, i acted cruelly, for i beat a puppy, i believe, simply from enjoying the sense of power; but the beating could not have been severe, for the puppy did not howl, of which i feel sure, as the spot was near the house. this act lay heavily on my conscience, as is shown by my remembering the exact spot where the crime was committed. it probably lay all the heavier from my love of dogs being then, and for a long time afterwards, a passion. dogs seemed to know this, for i was an adept in robbing their love from their masters. i remember clearly only one other incident during this year whilst at mr. case's daily school,--namely, the burial of a dragoon soldier; and it is surprising how clearly i can still see the horse with the man's empty boots and carbine suspended to the saddle, and the firing over the grave. this scene deeply stirred whatever poetic fancy there was in me. in the summer of 1818 i went to dr. butler's great school in shrewsbury, and remained there for seven years still midsummer 1825, when i was sixteen years old. i boarded at this school, so that i had the great advantage of living the life of a true schoolboy; but as the distance was hardly more than a mile to my home, i very often ran there in the longer intervals between the callings over and before locking up at night. this, i think, was in many ways advantageous to me by keeping up home affections and interests. i remember in the early part of my school life that i often had to run very quickly to be in time, and from being a fleet runner was generally successful; but when in doubt i prayed earnestly to god to help me, and i well remember that i attributed my success to the prayers and not to my quick running, and marvelled how generally i was aided. i have heard my father and elder sister say that i had, as a very young boy, a strong taste for long solitary walks; but what i thought about i know not. i often became quite absorbed, and once, whilst returning to school on the summit of the old fortifications round shrewsbury, which had been converted into a public foot-path with no parapet on one side, i walked off and fell to the ground, but the height was only seven or eight feet. nevertheless the number of thoughts which passed through my mind during this very short, but sudden and wholly unexpected fall, was astonishing, and seem hardly compatible with what physiologists have, i believe, proved about each thought requiring quite an appreciable amount of time. nothing could have been worse for the development of my mind than dr. butler's school, as it was strictly classical, nothing else being taught, except a little ancient geography and history. the school as a means of education to me was simply a blank. during my whole life i have been singularly incapable of mastering any language. especial attention was paid to verse-making, and this i could never do well. i had many friends, and got together a good collection of old verses, which by patching together, sometimes aided by other boys, i could work into any subject. much attention was paid to learning by heart the lessons of the previous day; this i could effect with great facility, learning forty or fifty lines of virgil or homer, whilst i was in morning chapel; but this exercise was utterly useless, for every verse was forgotten in forty-eight hours. i was not idle, and with the exception of versification, generally worked conscientiously at my classics, not using cribs. the sole pleasure i ever received from such studies, was from some of the odes of horace, which i admired greatly. when i left the school i was for my age neither high nor low in it; and i believe that i was considered by all my masters and by my father as a very ordinary boy, rather below the common standard in intellect. to my deep mortification my father once said to me, "you care for nothing but shooting, dogs, and rat-catching, and you will be a disgrace to yourself and all your family." but my father, who was the kindest man i ever knew and whose memory i love with all my heart, must have been angry and somewhat unjust when he used such words. looking back as well as i can at my character during my school life, the only qualities which at this period promised well for the future, were, that i had strong and diversified tastes, much zeal for whatever interested me, and a keen pleasure in understanding any complex subject or thing. i was taught euclid by a private tutor, and i distinctly remember the intense satisfaction which the clear geometrical proofs gave me. i remember, with equal distinctness, the delight which my uncle gave me (the father of francis galton) by explaining the principle of the vernier of a barometer with respect to diversified tastes, independently of science, i was fond of reading various books, and i used to sit for hours reading the historical plays of shakespeare, generally in an old window in the thick walls of the school. i read also other poetry, such as thomson's 'seasons,' and the recently published poems of byron and scott. i mention this because later in life i wholly lost, to my great regret, all pleasure from poetry of any kind, including shakespeare. in connection with pleasure from poetry, i may add that in 1822 a vivid delight in scenery was first awakened in my mind, during a riding tour on the borders of wales, and this has lasted longer than any other aesthetic pleasure. early in my school days a boy had a copy of the 'wonders of the world,' which i often read, and disputed with other boys about the veracity of some of the statements; and i believe that this book first gave me a wish to travel in remote countries, which was ultimately fulfilled by the voyage of the "beagle". in the latter part of my school life i became passionately fond of shooting; i do not believe that any one could have shown more zeal for the most holy cause than i did for shooting birds. how well i remember killing my first snipe, and my excitement was so great that i had much difficulty in reloading my gun from the trembling of my hands. this taste long continued, and i became a very good shot. when at cambridge i used to practise throwing up my gun to my shoulder before a looking-glass to see that i threw it up straight. another and better plan was to get a friend to wave about a lighted candle, and then to fire at it with a cap on the nipple, and if the aim was accurate the little puff of air would blow out the candle. the explosion of the cap caused a sharp crack, and i was told that the tutor of the college remarked, "what an extraordinary thing it is, mr. darwin seems to spend hours in cracking a horse-whip in his room, for i often hear the crack when i pass under his windows." i had many friends amongst the schoolboys, whom i loved dearly, and i think that my disposition was then very affectionate. with respect to science, i continued collecting minerals with much zeal, but quite unscientifically--all that i cared about was a new-_named_ mineral, and i hardly attempted to classify them. i must have observed insects with some little care, for when ten years old (1819) i went for three weeks to plas edwards on the sea-coast in wales, i was very much interested and surprised at seeing a large black and scarlet hemipterous insect, many moths (zygaena), and a cicindela which are not found in shropshire. i almost made up my mind to begin collecting all the insects which i could find dead, for on consulting my sister i concluded that it was not right to kill insects for the sake of making a collection. from reading white's 'selborne,' i took much pleasure in watching the habits of birds, and even made notes on the subject. in my simplicity i remember wondering why every gentleman did not become an ornithologist. towards the close of my school life, my brother worked hard at chemistry, and made a fair laboratory with proper apparatus in the tool-house in the garden, and i was allowed to aid him as a servant in most of his experiments. he made all the gases and many compounds, and i read with great care several books on chemistry, such as henry and parkes' 'chemical catechism.' the subject interested me greatly, and we often used to go on working till rather late at night. this was the best part of my education at school, for it showed me practically the meaning of experimental science. the fact that we worked at chemistry somehow got known at school, and as it was an unprecedented fact, i was nicknamed "gas." i was also once publicly rebuked by the head-master, dr. butler, for thus wasting my time on such useless subjects; and he called me very unjustly a "poco curante," and as i did not understand what he meant, it seemed to me a fearful reproach. as i was doing no good at school, my father wisely took me away at a rather earlier age than usual, and sent me (oct. 1825) to edinburgh university with my brother, where i stayed for two years or sessions. my brother was completing his medical studies, though i do not believe he ever really intended to practise, and i was sent there to commence them. but soon after this period i became convinced from various small circumstances that my father would leave me property enough to subsist on with some comfort, though i never imagined that i should be so rich a man as i am; but my belief was sufficient to check any strenuous efforts to learn medicine. the instruction at edinburgh was altogether by lectures, and these were intolerably dull, with the exception of those on chemistry by hope; but to my mind there are no advantages and many disadvantages in lectures compared with reading. dr. duncan's lectures on materia medica at 8 o'clock on a winter's morning are something fearful to remember. dr.---made his lectures on human anatomy as dull as he was himself, and the subject disgusted me. it has proved one of the greatest evils in my life that i was not urged to practise dissection, for i should soon have got over my disgust; and the practice would have been invaluable for all my future work. this has been an irremediable evil, as well as my incapacity to draw. i also attended regularly the clinical wards in the hospital. some of the cases distressed me a good deal, and i still have vivid pictures before me of some of them; but i was not so foolish as to allow this to lessen my attendance. i cannot understand why this part of my medical course did not interest me in a greater degree; for during the summer before coming to edinburgh i began attending some of the poor people, chiefly children and women in shrewsbury: i wrote down as full an account as i could of the case with all the symptoms, and read them aloud to my father, who suggested further inquiries and advised me what medicines to give, which i made up myself. at one time i had at least a dozen patients, and i felt a keen interest in the work. my father, who was by far the best judge of character whom i ever knew, declared that i should make a successful physician,--meaning by this one who would get many patients. he maintained that the chief element of success was exciting confidence; but what he saw in me which convinced him that i should create confidence i know not. i also attended on two occasions the operating theatre in the hospital at edinburgh, and saw two very bad operations, one on a child, but i rushed away before they were completed. nor did i ever attend again, for hardly any inducement would have been strong enough to make me do so; this being long before the blessed days of chloroform. the two cases fairly haunted me for many a long year. my brother stayed only one year at the university, so that during the second year i was left to my own resources; and this was an advantage, for i became well acquainted with several young men fond of natural science. one of these was ainsworth, who afterwards published his travels in assyria; he was a wernerian geologist, and knew a little about many subjects. dr. coldstream was a very different young man, prim, formal, highly religious, and most kind-hearted; he afterwards published some good zoological articles. a third young man was hardie, who would, i think, have made a good botanist, but died early in india. lastly, dr. grant, my senior by several years, but how i became acquainted with him i cannot remember; he published some first-rate zoological papers, but after coming to london as professor in university college, he did nothing more in science, a fact which has always been inexplicable to me. i knew him well; he was dry and formal in manner, with much enthusiasm beneath this outer crust. he one day, when we were walking together, burst forth in high admiration of lamarck and his views on evolution. i listened in silent astonishment, and as far as i can judge without any effect on my mind. i had previously read the 'zoonomia' of my grandfather, in which similar views are maintained, but without producing any effect on me. nevertheless it is probable that the hearing rather early in life such views maintained and praised may have favoured my upholding them under a different form in my 'origin of species.' at this time i admired greatly the 'zoonomia;' but on reading it a second time after an interval of ten or fifteen years, i was much disappointed; the proportion of speculation being so large to the facts given. drs. grant and coldstream attended much to marine zoology, and i often accompanied the former to collect animals in the tidal pools, which i dissected as well as i could. i also became friends with some of the newhaven fishermen, and sometimes accompanied them when they trawled for oysters, and thus got many specimens. but from not having had any regular practice in dissection, and from possessing only a wretched microscope, my attempts were very poor. nevertheless i made one interesting little discovery, and read, about the beginning of the year 1826, a short paper on the subject before the plinian society. this was that the so-called ova of flustra had the power of independent movement by means of cilia, and were in fact larvae. in another short paper i showed that the little globular bodies which had been supposed to be the young state of fucus loreus were the egg-cases of the wormlike pontobdella muricata. the plinian society was encouraged and, i believe, founded by professor jameson: it consisted of students and met in an underground room in the university for the sake of reading papers on natural science and discussing them. i used regularly to attend, and the meetings had a good effect on me in stimulating my zeal and giving me new congenial acquaintances. one evening a poor young man got up, and after stammering for a prodigious length of time, blushing crimson, he at last slowly got out the words, "mr. president, i have forgotten what i was going to say." the poor fellow looked quite overwhelmed, and all the members were so surprised that no one could think of a word to say to cover his confusion. the papers which were read to our little society were not printed, so that i had not the satisfaction of seeing my paper in print; but i believe dr. grant noticed my small discovery in his excellent memoir on flustra. i was also a member of the royal medical society, and attended pretty regularly; but as the subjects were exclusively medical, i did not much care about them. much rubbish was talked there, but there were some good speakers, of whom the best was the present sir j. kay-shuttleworth. dr. grant took me occasionally to the meetings of the wernerian society, where various papers on natural history were read, discussed, and afterwards published in the 'transactions.' i heard audubon deliver there some interesting discourses on the habits of n. american birds, sneering somewhat unjustly at waterton. by the way, a negro lived in edinburgh, who had travelled with waterton, and gained his livelihood by stuffing birds, which he did excellently: he gave me lessons for payment, and i used often to sit with him, for he was a very pleasant and intelligent man. mr. leonard horner also took me once to a meeting of the royal society of edinburgh, where i saw sir walter scott in the chair as president, and he apologised to the meeting as not feeling fitted for such a position. i looked at him and at the whole scene with some awe and reverence, and i think it was owing to this visit during my youth, and to my having attended the royal medical society, that i felt the honour of being elected a few years ago an honorary member of both these societies, more than any other similar honour. if i had been told at that time that i should one day have been thus honoured, i declare that i should have thought it as ridiculous and improbable, as if i had been told that i should be elected king of england. during my second year at edinburgh i attended ----'s lectures on geology and zoology, but they were incredibly dull. the sole effect they produced on me was the determination never as long as i lived to read a book on geology, or in any way to study the science. yet i feel sure that i was prepared for a philosophical treatment of the subject; for an old mr. cotton in shropshire, who knew a good deal about rocks, had pointed out to me two or three years previously a well-known large erratic boulder in the town of shrewsbury, called the "bell-stone"; he told me that there was no rock of the same kind nearer than cumberland or scotland, and he solemnly assured me that the world would come to an end before any one would be able to explain how this stone came where it now lay. this produced a deep impression on me, and i meditated over this wonderful stone. so that i felt the keenest delight when i first read of the action of icebergs in transporting boulders, and i gloried in the progress of geology. equally striking is the fact that i, though now only sixty-seven years old, heard the professor, in a field lecture at salisbury craigs, discoursing on a trapdyke, with amygdaloidal margins and the strata indurated on each side, with volcanic rocks all around us, say that it was a fissure filled with sediment from above, adding with a sneer that there were men who maintained that it had been injected from beneath in a molten condition. when i think of this lecture, i do not wonder that i determined never to attend to geology. from attending ----'s lectures, i became acquainted with the curator of the museum, mr. macgillivray, who afterwards published a large and excellent book on the birds of scotland. i had much interesting natural-history talk with him, and he was very kind to me. he gave me some rare shells, for i at that time collected marine mollusca, but with no great zeal. my summer vacations during these two years were wholly given up to amusements, though i always had some book in hand, which i read with interest. during the summer of 1826 i took a long walking tour with two friends with knapsacks on our backs through north wales. we walked thirty miles most days, including one day the ascent of snowdon. i also went with my sister a riding tour in north wales, a servant with saddle-bags carrying our clothes. the autumns were devoted to shooting chiefly at mr. owen's, at woodhouse, and at my uncle jos's (josiah wedgwood, the son of the founder of the etruria works.) at maer. my zeal was so great that i used to place my shooting-boots open by my bed-side when i went to bed, so as not to lose half a minute in putting them on in the morning; and on one occasion i reached a distant part of the maer estate, on the 20th of august for black-game shooting, before i could see: i then toiled on with the game-keeper the whole day through thick heath and young scotch firs. i kept an exact record of every bird which i shot throughout the whole season. one day when shooting at woodhouse with captain owen, the eldest son, and major hill, his cousin, afterwards lord berwick, both of whom i liked very much, i thought myself shamefully used, for every time after i had fired and thought that i had killed a bird, one of the two acted as if loading his gun, and cried out, "you must not count that bird, for i fired at the same time," and the gamekeeper, perceiving the joke, backed them up. after some hours they told me the joke, but it was no joke to me, for i had shot a large number of birds, but did not know how many, and could not add them to my list, which i used to do by making a knot in a piece of string tied to a button-hole. this my wicked friends had perceived. how i did enjoy shooting! but i think that i must have been half-consciously ashamed of my zeal, for i tried to persuade myself that shooting was almost an intellectual employment; it required so much skill to judge where to find most game and to hunt the dogs well. one of my autumnal visits to maer in 1827 was memorable from meeting there sir j. mackintosh, who was the best converser i ever listened to. i heard afterwards with a glow of pride that he had said, "there is something in that young man that interests me." this must have been chiefly due to his perceiving that i listened with much interest to everything which he said, for i was as ignorant as a pig about his subjects of history, politics, and moral philosophy. to hear of praise from an eminent person, though no doubt apt or certain to excite vanity, is, i think, good for a young man, as it helps to keep him in the right course. my visits to maer during these two or three succeeding years were quite delightful, independently of the autumnal shooting. life there was perfectly free; the country was very pleasant for walking or riding; and in the evening there was much very agreeable conversation, not so personal as it generally is in large family parties, together with music. in the summer the whole family used often to sit on the steps of the old portico, with the flower-garden in front, and with the steep wooded bank opposite the house reflected in the lake, with here and there a fish rising or a water-bird paddling about. nothing has left a more vivid picture on my mind than these evenings at maer. i was also attached to and greatly revered my uncle jos; he was silent and reserved, so as to be a rather awful man; but he sometimes talked openly with me. he was the very type of an upright man, with the clearest judgment. i do not believe that any power on earth could have made him swerve an inch from what he considered the right course. i used to apply to him in my mind the well-known ode of horace, now forgotten by me, in which the words "nec vultus tyranni, etc.," come in. (justum et tenacem propositi virum non civium ardor prava jubentium non vultus instantis tyranni mente quatit solida.) cambridge 1828-1831. after having spent two sessions in edinburgh, my father perceived, or he heard from my sisters, that i did not like the thought of being a physician, so he proposed that i should become a clergyman. he was very properly vehement against my turning into an idle sporting man, which then seemed my probable destination. i asked for some time to consider, as from what little i had heard or thought on the subject i had scruples about declaring my belief in all the dogmas of the church of england; though otherwise i liked the thought of being a country clergyman. accordingly i read with care 'pearson on the creed,' and a few other books on divinity; and as i did not then in the least doubt the strict and literal truth of every word in the bible, i soon persuaded myself that our creed must be fully accepted. considering how fiercely i have been attacked by the orthodox, it seems ludicrous that i once intended to be a clergyman. nor was this intention and my father's wish ever formerly given up, but died a natural death when, on leaving cambridge, i joined the "beagle" as naturalist. if the phrenologists are to be trusted, i was well fitted in one respect to be a clergyman. a few years ago the secretaries of a german psychological society asked me earnestly by letter for a photograph of myself; and some time afterwards i received the proceedings of one of the meetings, in which it seemed that the shape of my head had been the subject of a public discussion, and one of the speakers declared that i had the bump of reverence developed enough for ten priests. as it was decided that i should be a clergyman, it was necessary that i should go to one of the english universities and take a degree; but as i had never opened a classical book since leaving school, i found to my dismay, that in the two intervening years i had actually forgotten, incredible as it may appear, almost everything which i had learnt, even to some few of the greek letters. i did not therefore proceed to cambridge at the usual time in october, but worked with a private tutor in shrewsbury, and went to cambridge after the christmas vacation, early in 1828. i soon recovered my school standard of knowledge, and could translate easy greek books, such as homer and the greek testament, with moderate facility. during the three years which i spent at cambridge my time was wasted, as far as the academical studies were concerned, as completely as at edinburgh and at school. i attempted mathematics, and even went during the summer of 1828 with a private tutor (a very dull man) to barmouth, but i got on very slowly. the work was repugnant to me, chiefly from my not being able to see any meaning in the early steps in algebra. this impatience was very foolish, and in after years i have deeply regretted that i did not proceed far enough at least to understand something of the great leading principles of mathematics, for men thus endowed seem to have an extra sense. but i do not believe that i should ever have succeeded beyond a very low grade. with respect to classics i did nothing except attend a few compulsory college lectures, and the attendance was almost nominal. in my second year i had to work for a month or two to pass the little-go, which i did easily. again, in my last year i worked with some earnestness for my final degree of b.a., and brushed up my classics, together with a little algebra and euclid, which latter gave me much pleasure, as it did at school. in order to pass the b.a. examination, it was also necessary to get up paley's 'evidences of christianity,' and his 'moral philosophy.' this was done in a thorough manner, and i am convinced that i could have written out the whole of the 'evidences' with perfect correctness, but not of course in the clear language of paley. the logic of this book and, as i may add, of his 'natural theology,' gave me as much delight as did euclid. the careful study of these works, without attempting to learn any part by rote, was the only part of the academical course which, as i then felt and as i still believe, was of the least use to me in the education of my mind. i did not at that time trouble myself about paley's premises; and taking these on trust, i was charmed and convinced by the long line of argumentation. by answering well the examination questions in paley, by doing euclid well, and by not failing miserably in classics, i gained a good place among the oi polloi or crowd of men who do not go in for honours. oddly enough, i cannot remember how high i stood, and my memory fluctuates between the fifth, tenth, or twelfth, name on the list. (tenth in the list of january 1831.) public lectures on several branches were given in the university, attendance being quite voluntary; but i was so sickened with lectures at edinburgh that i did not even attend sedgwick's eloquent and interesting lectures. had i done so i should probably have become a geologist earlier than i did. i attended, however, henslow's lectures on botany, and liked them much for their extreme clearness, and the admirable illustrations; but i did not study botany. henslow used to take his pupils, including several of the older members of the university, field excursions, on foot or in coaches, to distant places, or in a barge down the river, and lectured on the rarer plants and animals which were observed. these excursions were delightful. although, as we shall presently see, there were some redeeming features in my life at cambridge, my time was sadly wasted there, and worse than wasted. from my passion for shooting and for hunting, and, when this failed, for riding across country, i got into a sporting set, including some dissipated low-minded young men. we used often to dine together in the evening, though these dinners often included men of a higher stamp, and we sometimes drank too much, with jolly singing and playing at cards afterwards. i know that i ought to feel ashamed of days and evenings thus spent, but as some of my friends were very pleasant, and we were all in the highest spirits, i cannot help looking back to these times with much pleasure. but i am glad to think that i had many other friends of a widely different nature. i was very intimate with whitley (rev. c. whitley, hon. canon of durham, formerly reader in natural philosophy in durham university.), who was afterwards senior wrangler, and we used continually to take long walks together. he inoculated me with a taste for pictures and good engravings, of which i bought some. i frequently went to the fitzwilliam gallery, and my taste must have been fairly good, for i certainly admired the best pictures, which i discussed with the old curator. i read also with much interest sir joshua reynolds' book. this taste, though not natural to me, lasted for several years, and many of the pictures in the national gallery in london gave me much pleasure; that of sebastian del piombo exciting in me a sense of sublimity. i also got into a musical set, i believe by means of my warm-hearted friend, herbert (the late john maurice herbert, county court judge of cardiff and the monmouth circuit.), who took a high wrangler's degree. from associating with these men, and hearing them play, i acquired a strong taste for music, and used very often to time my walks so as to hear on week days the anthem in king's college chapel. this gave me intense pleasure, so that my backbone would sometimes shiver. i am sure that there was no affectation or mere imitation in this taste, for i used generally to go by myself to king's college, and i sometimes hired the chorister boys to sing in my rooms. nevertheless i am so utterly destitute of an ear, that i cannot perceive a discord, or keep time and hum a tune correctly; and it is a mystery how i could possibly have derived pleasure from music. my musical friends soon perceived my state, and sometimes amused themselves by making me pass an examination, which consisted in ascertaining how many tunes i could recognise when they were played rather more quickly or slowly than usual. 'god save the king,' when thus played, was a sore puzzle. there was another man with almost as bad an ear as i had, and strange to say he played a little on the flute. once i had the triumph of beating him in one of our musical examinations. but no pursuit at cambridge was followed with nearly so much eagerness or gave me so much pleasure as collecting beetles. it was the mere passion for collecting, for i did not dissect them, and rarely compared their external characters with published descriptions, but got them named anyhow. i will give a proof of my zeal: one day, on tearing off some old bark, i saw two rare beetles, and seized one in each hand; then i saw a third and new kind, which i could not bear to lose, so that i popped the one which i held in my right hand into my mouth. alas! it ejected some intensely acrid fluid, which burnt my tongue so that i was forced to spit the beetle out, which was lost, as was the third one. i was very successful in collecting, and invented two new methods; i employed a labourer to scrape during the winter, moss off old trees and place it in a large bag, and likewise to collect the rubbish at the bottom of the barges in which reeds are brought from the fens, and thus i got some very rare species. no poet ever felt more delighted at seeing his first poem published than i did at seeing, in stephens' 'illustrations of british insects,' the magic words, "captured by c. darwin, esq." i was introduced to entomology by my second cousin w. darwin fox, a clever and most pleasant man, who was then at christ's college, and with whom i became extremely intimate. afterwards i became well acquainted, and went out collecting, with albert way of trinity, who in after years became a well-known archaeologist; also with h. thompson of the same college, afterwards a leading agriculturist, chairman of a great railway, and member of parliament. it seems therefore that a taste for collecting beetles is some indication of future success in life! i am surprised what an indelible impression many of the beetles which i caught at cambridge have left on my mind. i can remember the exact appearance of certain posts, old trees and banks where i made a good capture. the pretty panagaeus crux-major was a treasure in those days, and here at down i saw a beetle running across a walk, and on picking it up instantly perceived that it differed slightly from p. crux-major, and it turned out to be p. quadripunctatus, which is only a variety or closely allied species, differing from it very slightly in outline. i had never seen in those old days licinus alive, which to an uneducated eye hardly differs from many of the black carabidous beetles; but my sons found here a specimen, and i instantly recognised that it was new to me; yet i had not looked at a british beetle for the last twenty years. i have not as yet mentioned a circumstance which influenced my whole career more than any other. this was my friendship with professor henslow. before coming up to cambridge, i had heard of him from my brother as a man who knew every branch of science, and i was accordingly prepared to reverence him. he kept open house once every week when all undergraduates, and some older members of the university, who were attached to science, used to meet in the evening. i soon got, through fox, an invitation, and went there regularly. before long i became well acquainted with henslow, and during the latter half of my time at cambridge took long walks with him on most days; so that i was called by some of the dons "the man who walks with henslow;" and in the evening i was very often asked to join his family dinner. his knowledge was great in botany, entomology, chemistry, mineralogy, and geology. his strongest taste was to draw conclusions from long-continued minute observations. his judgment was excellent, and his whole mind well balanced; but i do not suppose that any one would say that he possessed much original genius. he was deeply religious, and so orthodox that he told me one day he should be grieved if a single word of the thirty-nine articles were altered. his moral qualities were in every way admirable. he was free from every tinge of vanity or other petty feeling; and i never saw a man who thought so little about himself or his own concerns. his temper was imperturbably good, with the most winning and courteous manners; yet, as i have seen, he could be roused by any bad action to the warmest indignation and prompt action. i once saw in his company in the streets of cambridge almost as horrid a scene as could have been witnessed during the french revolution. two body-snatchers had been arrested, and whilst being taken to prison had been torn from the constable by a crowd of the roughest men, who dragged them by their legs along the muddy and stony road. they were covered from head to foot with mud, and their faces were bleeding either from having been kicked or from the stones; they looked like corpses, but the crowd was so dense that i got only a few momentary glimpses of the wretched creatures. never in my life have i seen such wrath painted on a man's face as was shown by henslow at this horrid scene. he tried repeatedly to penetrate the mob; but it was simply impossible. he then rushed away to the mayor, telling me not to follow him, but to get more policemen. i forget the issue, except that the two men were got into the prison without being killed. henslow's benevolence was unbounded, as he proved by his many excellent schemes for his poor parishioners, when in after years he held the living of hitcham. my intimacy with such a man ought to have been, and i hope was, an inestimable benefit. i cannot resist mentioning a trifling incident, which showed his kind consideration. whilst examining some pollen-grains on a damp surface, i saw the tubes exserted, and instantly rushed off to communicate my surprising discovery to him. now i do not suppose any other professor of botany could have helped laughing at my coming in such a hurry to make such a communication. but he agreed how interesting the phenomenon was, and explained its meaning, but made me clearly understand how well it was known; so i left him not in the least mortified, but well pleased at having discovered for myself so remarkable a fact, but determined not to be in such a hurry again to communicate my discoveries. dr. whewell was one of the older and distinguished men who sometimes visited henslow, and on several occasions i walked home with him at night. next to sir j. mackintosh he was the best converser on grave subjects to whom i ever listened. leonard jenyns (the well-known soame jenyns was cousin to mr. jenyns' father.), who afterwards published some good essays in natural history (mr. jenyns (now blomefield) described the fish for the zoology of the "beagle"; and is author of a long series of papers, chiefly zoological.), often stayed with henslow, who was his brother-in-law. i visited him at his parsonage on the borders of the fens [swaffham bulbeck], and had many a good walk and talk with him about natural history. i became also acquainted with several other men older than me, who did not care much about science, but were friends of henslow. one was a scotchman, brother of sir alexander ramsay, and tutor of jesus college: he was a delightful man, but did not live for many years. another was mr. dawes, afterwards dean of hereford, and famous for his success in the education of the poor. these men and others of the same standing, together with henslow, used sometimes to take distant excursions into the country, which i was allowed to join, and they were most agreeable. looking back, i infer that there must have been something in me a little superior to the common run of youths, otherwise the above-mentioned men, so much older than me and higher in academical position, would never have allowed me to associate with them. certainly i was not aware of any such superiority, and i remember one of my sporting friends, turner, who saw me at work with my beetles, saying that i should some day be a fellow of the royal society, and the notion seemed to me preposterous. during my last year at cambridge, i read with care and profound interest humboldt's 'personal narrative.' this work, and sir j. herschel's 'introduction to the study of natural philosophy,' stirred up in me a burning zeal to add even the most humble contribution to the noble structure of natural science. no one or a dozen other books influenced me nearly so much as these two. i copied out from humboldt long passages about teneriffe, and read them aloud on one of the above-mentioned excursions, to (i think) henslow, ramsay, and dawes, for on a previous occasion i had talked about the glories of teneriffe, and some of the party declared they would endeavour to go there; but i think that they were only half in earnest. i was, however, quite in earnest, and got an introduction to a merchant in london to enquire about ships; but the scheme was, of course, knocked on the head by the voyage of the "beagle". my summer vacations were given up to collecting beetles, to some reading, and short tours. in the autumn my whole time was devoted to shooting, chiefly at woodhouse and maer, and sometimes with young eyton of eyton. upon the whole the three years which i spent at cambridge were the most joyful in my happy life; for i was then in excellent health, and almost always in high spirits. as i had at first come up to cambridge at christmas, i was forced to keep two terms after passing my final examination, at the commencement of 1831; and henslow then persuaded me to begin the study of geology. therefore on my return to shropshire i examined sections, and coloured a map of parts round shrewsbury. professor sedgwick intended to visit north wales in the beginning of august to pursue his famous geological investigations amongst the older rocks, and henslow asked him to allow me to accompany him. (in connection with this tour my father used to tell a story about sedgwick: they had started from their inn one morning, and had walked a mile or two, when sedgwick suddenly stopped, and vowed that he would return, being certain "that damned scoundrel" (the waiter) had not given the chambermaid the sixpence intrusted to him for the purpose. he was ultimately persuaded to give up the project, seeing that there was no reason for suspecting the waiter of especial perfidy.--f.d.) accordingly he came and slept at my father's house. a short conversation with him during this evening produced a strong impression on my mind. whilst examining an old gravel-pit near shrewsbury, a labourer told me that he had found in it a large worn tropical volute shell, such as may be seen on the chimney-pieces of cottages; and as he would not sell the shell, i was convinced that he had really found it in the pit. i told sedgwick of the fact, and he at once said (no doubt truly) that it must have been thrown away by some one into the pit; but then added, if really embedded there it would be the greatest misfortune to geology, as it would overthrow all that we know about the superficial deposits of the midland counties. these gravel-beds belong in fact to the glacial period, and in after years i found in them broken arctic shells. but i was then utterly astonished at sedgwick not being delighted at so wonderful a fact as a tropical shell being found near the surface in the middle of england. nothing before had ever made me thoroughly realise, though i had read various scientific books, that science consists in grouping facts so that general laws or conclusions may be drawn from them. next morning we started for llangollen, conway, bangor, and capel curig. this tour was of decided use in teaching me a little how to make out the geology of a country. sedgwick often sent me on a line parallel to his, telling me to bring back specimens of the rocks and to mark the stratification on a map. i have little doubt that he did this for my good, as i was too ignorant to have aided him. on this tour i had a striking instance of how easy it is to overlook phenomena, however conspicuous, before they have been observed by any one. we spent many hours in cwm idwal, examining all the rocks with extreme care, as sedgwick was anxious to find fossils in them; but neither of us saw a trace of the wonderful glacial phenomena all around us; we did not notice the plainly scored rocks, the perched boulders, the lateral and terminal moraines. yet these phenomena are so conspicuous that, as i declared in a paper published many years afterwards in the 'philosophical magazine' ('philosophical magazine,' 1842.), a house burnt down by fire did not tell its story more plainly than did this valley. if it had still been filled by a glacier, the phenomena would have been less distinct than they now are. at capel curig i left sedgwick and went in a straight line by compass and map across the mountains to barmouth, never following any track unless it coincided with my course. i thus came on some strange wild places, and enjoyed much this manner of travelling. i visited barmouth to see some cambridge friends who were reading there, and thence returned to shrewsbury and to maer for shooting; for at that time i should have thought myself mad to give up the first days of partridge-shooting for geology or any other science. "voyage of the 'beagle' from december 27, 1831, to october 2, 1836." on returning home from my short geological tour in north wales, i found a letter from henslow, informing me that captain fitz-roy was willing to give up part of his own cabin to any young man who would volunteer to go with him without pay as naturalist to the voyage of the "beagle". i have given, as i believe, in my ms. journal an account of all the circumstances which then occurred; i will here only say that i was instantly eager to accept the offer, but my father strongly objected, adding the words, fortunate for me, "if you can find any man of common sense who advises you to go i will give my consent." so i wrote that evening and refused the offer. on the next morning i went to maer to be ready for september 1st, and, whilst out shooting, my uncle (josiah wedgwood.) sent for me, offering to drive me over to shrewsbury and talk with my father, as my uncle thought it would be wise in me to accept the offer. my father always maintained that he was one of the most sensible men in the world, and he at once consented in the kindest manner. i had been rather extravagant at cambridge, and to console my father, said, "that i should be deuced clever to spend more than my allowance whilst on board the 'beagle';" but he answered with a smile, "but they tell me you are very clever." next day i started for cambridge to see henslow, and thence to london to see fitz-roy, and all was soon arranged. afterwards, on becoming very intimate with fitz-roy, i heard that i had run a very narrow risk of being rejected, on account of the shape of my nose! he was an ardent disciple of lavater, and was convinced that he could judge of a man's character by the outline of his features; and he doubted whether any one with my nose could possess sufficient energy and determination for the voyage. but i think he was afterwards well satisfied that my nose had spoken falsely. fitz-roy's character was a singular one, with very many noble features: he was devoted to his duty, generous to a fault, bold, determined, and indomitably energetic, and an ardent friend to all under his sway. he would undertake any sort of trouble to assist those whom he thought deserved assistance. he was a handsome man, strikingly like a gentleman, with highly courteous manners, which resembled those of his maternal uncle, the famous lord castlereagh, as i was told by the minister at rio. nevertheless he must have inherited much in his appearance from charles ii., for dr. wallich gave me a collection of photographs which he had made, and i was struck with the resemblance of one to fitz-roy; and on looking at the name, i found it ch. e. sobieski stuart, count d'albanie, a descendant of the same monarch. fitz-roy's temper was a most unfortunate one. it was usually worst in the early morning, and with his eagle eye he could generally detect something amiss about the ship, and was then unsparing in his blame. he was very kind to me, but was a man very difficult to live with on the intimate terms which necessarily followed from our messing by ourselves in the same cabin. we had several quarrels; for instance, early in the voyage at bahia, in brazil, he defended and praised slavery, which i abominated, and told me that he had just visited a great slave-owner, who had called up many of his slaves and asked them whether they were happy, and whether they wished to be free, and all answered "no." i then asked him, perhaps with a sneer, whether he thought that the answer of slaves in the presence of their master was worth anything? this made him excessively angry, and he said that as i doubted his word we could not live any longer together. i thought that i should have been compelled to leave the ship; but as soon as the news spread, which it did quickly, as the captain sent for the first lieutenant to assuage his anger by abusing me, i was deeply gratified by receiving an invitation from all the gun-room officers to mess with them. but after a few hours fitz-roy showed his usual magnanimity by sending an officer to me with an apology and a request that i would continue to live with him. his character was in several respects one of the most noble which i have ever known. the voyage of the "beagle" has been by far the most important event in my life, and has determined my whole career; yet it depended on so small a circumstance as my uncle offering to drive me thirty miles to shrewsbury, which few uncles would have done, and on such a trifle as the shape of my nose. i have always felt that i owe to the voyage the first real training or education of my mind; i was led to attend closely to several branches of natural history, and thus my powers of observation were improved, though they were always fairly developed. the investigation of the geology of all the places visited was far more important, as reasoning here comes into play. on first examining a new district nothing can appear more hopeless than the chaos of rocks; but by recording the stratification and nature of the rocks and fossils at many points, always reasoning and predicting what will be found elsewhere, light soon begins to dawn on the district, and the structure of the whole becomes more or less intelligible. i had brought with me the first volume of lyell's 'principles of geology,' which i studied attentively; and the book was of the highest service to me in many ways. the very first place which i examined, namely st. jago in the cape de verde islands, showed me clearly the wonderful superiority of lyell's manner of treating geology, compared with that of any other author, whose works i had with me or ever afterwards read. another of my occupations was collecting animals of all classes, briefly describing and roughly dissecting many of the marine ones; but from not being able to draw, and from not having sufficient anatomical knowledge, a great pile of ms. which i made during the voyage has proved almost useless. i thus lost much time, with the exception of that spent in acquiring some knowledge of the crustaceans, as this was of service when in after years i undertook a monograph of the cirripedia. during some part of the day i wrote my journal, and took much pains in describing carefully and vividly all that i had seen; and this was good practice. my journal served also, in part, as letters to my home, and portions were sent to england whenever there was an opportunity. the above various special studies were, however, of no importance compared with the habit of energetic industry and of concentrated attention to whatever i was engaged in, which i then acquired. everything about which i thought or read was made to bear directly on what i had seen or was likely to see; and this habit of mind was continued during the five years of the voyage. i feel sure that it was this training which has enabled me to do whatever i have done in science. looking backwards, i can now perceive how my love for science gradually preponderated over every other taste. during the first two years my old passion for shooting survived in nearly full force, and i shot myself all the birds and animals for my collection; but gradually i gave up my gun more and more, and finally altogether, to my servant, as shooting interfered with my work, more especially with making out the geological structure of a country. i discovered, though unconsciously and insensibly, that the pleasure of observing and reasoning was a much higher one than that of skill and sport. that my mind became developed through my pursuits during the voyage is rendered probable by a remark made by my father, who was the most acute observer whom i ever saw, of a sceptical disposition, and far from being a believer in phrenology; for on first seeing me after the voyage, he turned round to my sisters, and exclaimed, "why, the shape of his head is quite altered." to return to the voyage. on september 11th (1831), i paid a flying visit with fitz-roy to the "beagle" at plymouth. thence to shrewsbury to wish my father and sisters a long farewell. on october 24th i took up my residence at plymouth, and remained there until december 27th, when the "beagle" finally left the shores of england for her circumnavigation of the world. we made two earlier attempts to sail, but were driven back each time by heavy gales. these two months at plymouth were the most miserable which i ever spent, though i exerted myself in various ways. i was out of spirits at the thought of leaving all my family and friends for so long a time, and the weather seemed to me inexpressibly gloomy. i was also troubled with palpitation and pain about the heart, and like many a young ignorant man, especially one with a smattering of medical knowledge, was convinced that i had heart disease. i did not consult any doctor, as i fully expected to hear the verdict that i was not fit for the voyage, and i was resolved to go at all hazards. i need not here refer to the events of the voyage--where we went and what we did--as i have given a sufficiently full account in my published journal. the glories of the vegetation of the tropics rise before my mind at the present time more vividly than anything else; though the sense of sublimity, which the great deserts of patagonia and the forest-clad mountains of tierra del fuego excited in me, has left an indelible impression on my mind. the sight of a naked savage in his native land is an event which can never be forgotten. many of my excursions on horseback through wild countries, or in the boats, some of which lasted several weeks, were deeply interesting: their discomfort and some degree of danger were at that time hardly a drawback, and none at all afterwards. i also reflect with high satisfaction on some of my scientific work, such as solving the problem of coral islands, and making out the geological structure of certain islands, for instance, st. helena. nor must i pass over the discovery of the singular relations of the animals and plants inhabiting the several islands of the galapagos archipelago, and of all of them to the inhabitants of south america. as far as i can judge of myself, i worked to the utmost during the voyage from the mere pleasure of investigation, and from my strong desire to add a few facts to the great mass of facts in natural science. but i was also ambitious to take a fair place among scientific men,--whether more ambitious or less so than most of my fellow-workers, i can form no opinion. the geology of st. jago is very striking, yet simple: a stream of lava formerly flowed over the bed of the sea, formed of triturated recent shells and corals, which it has baked into a hard white rock. since then the whole island has been upheaved. but the line of white rock revealed to me a new and important fact, namely, that there had been afterwards subsidence round the craters, which had since been in action, and had poured forth lava. it then first dawned on me that i might perhaps write a book on the geology of the various countries visited, and this made me thrill with delight. that was a memorable hour to me, and how distinctly i can call to mind the low cliff of lava beneath which i rested, with the sun glaring hot, a few strange desert plants growing near, and with living corals in the tidal pools at my feet. later in the voyage, fitz-roy asked me to read some of my journal, and declared it would be worth publishing; so here was a second book in prospect! towards the close of our voyage i received a letter whilst at ascension, in which my sisters told me that sedgwick had called on my father, and said that i should take a place among the leading scientific men. i could not at the time understand how he could have learnt anything of my proceedings, but i heard (i believe afterwards) that henslow had read some of the letters which i wrote to him before the philosophical society of cambridge (read at the meeting held november 16, 1835, and printed in a pamphlet of 31 pages for distribution among the members of the society.), and had printed them for private distribution. my collection of fossil bones, which had been sent to henslow, also excited considerable attention amongst palaeontologists. after reading this letter, i clambered over the mountains of ascension with a bounding step, and made the volcanic rocks resound under my geological hammer. all this shows how ambitious i was; but i think that i can say with truth that in after years, though i cared in the highest degree for the approbation of such men as lyell and hooker, who were my friends, i did not care much about the general public. i do not mean to say that a favourable review or a large sale of my books did not please me greatly, but the pleasure was a fleeting one, and i am sure that i have never turned one inch out of my course to gain fame. from my return to england (october 2, 1836) to my marriage (january 29, 1839.) these two years and three months were the most active ones which i ever spent, though i was occasionally unwell, and so lost some time. after going backwards and forwards several times between shrewsbury, maer, cambridge, and london, i settled in lodgings at cambridge (in fitzwilliam street.) on december 13th, where all my collections were under the care of henslow. i stayed here three months, and got my minerals and rocks examined by the aid of professor miller. i began preparing my 'journal of travels,' which was not hard work, as my ms. journal had been written with care, and my chief labour was making an abstract of my more interesting scientific results. i sent also, at the request of lyell, a short account of my observations on the elevation of the coast of chile to the geological society. ('geolog. soc. proc. ii. 1838, pages 446-449.) on march 7th, 1837, i took lodgings in great marlborough street in london, and remained there for nearly two years, until i was married. during these two years i finished my journal, read several papers before the geological society, began preparing the ms. for my 'geological observations,' and arranged for the publication of the 'zoology of the voyage of the "beagle".' in july i opened my first note-book for facts in relation to the origin of species, about which i had long reflected, and never ceased working for the next twenty years. during these two years i also went a little into society, and acted as one of the honorary secretaries of the geological society. i saw a great deal of lyell. one of his chief characteristics was his sympathy with the work of others, and i was as much astonished as delighted at the interest which he showed when, on my return to england, i explained to him my views on coral reefs. this encouraged me greatly, and his advice and example had much influence on me. during this time i saw also a good deal of robert brown; i used often to call and sit with him during his breakfast on sunday mornings, and he poured forth a rich treasure of curious observations and acute remarks, but they almost always related to minute points, and he never with me discussed large or general questions in science. during these two years i took several short excursions as a relaxation, and one longer one to the parallel roads of glen roy, an account of which was published in the 'philosophical transactions.' (1839, pages 39-82.) this paper was a great failure, and i am ashamed of it. having been deeply impressed with what i had seen of the elevation of the land of south america, i attributed the parallel lines to the action of the sea; but i had to give up this view when agassiz propounded his glacier-lake theory. because no other explanation was possible under our then state of knowledge, i argued in favour of sea-action; and my error has been a good lesson to me never to trust in science to the principle of exclusion. as i was not able to work all day at science, i read a good deal during these two years on various subjects, including some metaphysical books; but i was not well fitted for such studies. about this time i took much delight in wordsworth's and coleridge's poetry; and can boast that i read the 'excursion' twice through. formerly milton's 'paradise lost' had been my chief favourite, and in my excursions during the voyage of the "beagle", when i could take only a single volume, i always chose milton. from my marriage, january 29, 1839, and residence in upper gower street, to our leaving london and settling at down, september 14, 1842. (after speaking of his happy married life, and of his children, he continues:--) during the three years and eight months whilst we resided in london, i did less scientific work, though i worked as hard as i possibly could, than during any other equal length of time in my life. this was owing to frequently recurring unwellness, and to one long and serious illness. the greater part of my time, when i could do anything, was devoted to my work on 'coral reefs,' which i had begun before my marriage, and of which the last proof-sheet was corrected on may 6th, 1842. this book, though a small one, cost me twenty months of hard work, as i had to read every work on the islands of the pacific and to consult many charts. it was thought highly of by scientific men, and the theory therein given is, i think, now well established. no other work of mine was begun in so deductive a spirit as this, for the whole theory was thought out on the west coast of south america, before i had seen a true coral reef. i had therefore only to verify and extend my views by a careful examination of living reefs. but it should be observed that i had during the two previous years been incessantly attending to the effects on the shores of south america of the intermittent elevation of the land, together with denudation and the deposition of sediment. this necessarily led me to reflect much on the effects of subsidence, and it was easy to replace in imagination the continued deposition of sediment by the upward growth of corals. to do this was to form my theory of the formation of barrier-reefs and atolls. besides my work on coral-reefs, during my residence in london, i read before the geological society papers on the erratic boulders of south america ('geolog. soc. proc.' iii. 1842.), on earthquakes ('geolog. trans. v. 1840.), and on the formation by the agency of earth-worms of mould. ('geolog. soc. proc. ii. 1838.) i also continued to superintend the publication of the 'zoology of the voyage of the "beagle".' nor did i ever intermit collecting facts bearing on the origin of species; and i could sometimes do this when i could do nothing else from illness. in the summer of 1842 i was stronger than i had been for some time, and took a little tour by myself in north wales, for the sake of observing the effects of the old glaciers which formerly filled all the larger valleys. i published a short account of what i saw in the 'philosophical magazine.' ('philosophical magazine,' 1842.) this excursion interested me greatly, and it was the last time i was ever strong enough to climb mountains or to take long walks such as are necessary for geological work. during the early part of our life in london, i was strong enough to go into general society, and saw a good deal of several scientific men, and other more or less distinguished men. i will give my impressions with respect to some of them, though i have little to say worth saying. i saw more of lyell than of any other man, both before and after my marriage. his mind was characterised, as it appeared to me, by clearness, caution, sound judgment, and a good deal of originality. when i made any remark to him on geology, he never rested until he saw the whole case clearly, and often made me see it more clearly than i had done before. he would advance all possible objections to my suggestion, and even after these were exhausted would long remain dubious. a second characteristic was his hearty sympathy with the work of other scientific men. (the slight repetition here observable is accounted for by the notes on lyell, etc., having been added in april, 1881, a few years after the rest of the 'recollections' were written.) on my return from the voyage of the "beagle", i explained to him my views on coral-reefs, which differed from his, and i was greatly surprised and encouraged by the vivid interest which he showed. his delight in science was ardent, and he felt the keenest interest in the future progress of mankind. he was very kind-hearted, and thoroughly liberal in his religious beliefs, or rather disbeliefs; but he was a strong theist. his candour was highly remarkable. he exhibited this by becoming a convert to the descent theory, though he had gained much fame by opposing lamarck's views, and this after he had grown old. he reminded me that i had many years before said to him, when discussing the opposition of the old school of geologists to his new views, "what a good thing it would be if every scientific man was to die when sixty years old, as afterwards he would be sure to oppose all new doctrines." but he hoped that now he might be allowed to live. the science of geology is enormously indebted to lyell--more so, as i believe, than to any other man who ever lived. when [i was] starting on the voyage of the "beagle", the sagacious henslow, who, like all other geologists, believed at that time in successive cataclysms, advised me to get and study the first volume of the 'principles,' which had then just been published, but on no account to accept the views therein advocated. how differently would anyone now speak of the 'principles'! i am proud to remember that the first place, namely, st. jago, in the cape de verde archipelago, in which i geologised, convinced me of the infinite superiority of lyell's views over those advocated in any other work known to me. the powerful effects of lyell's works could formerly be plainly seen in the different progress of the science in france and england. the present total oblivion of elie de beaumont's wild hypotheses, such as his 'craters of elevation' and 'lines of elevation' (which latter hypothesis i heard sedgwick at the geological society lauding to the skies), may be largely attributed to lyell. i saw a good deal of robert brown, "facile princeps botanicorum," as he was called by humboldt. he seemed to me to be chiefly remarkable for the minuteness of his observations, and their perfect accuracy. his knowledge was extraordinarily great, and much died with him, owing to his excessive fear of ever making a mistake. he poured out his knowledge to me in the most unreserved manner, yet was strangely jealous on some points. i called on him two or three times before the voyage of the "beagle", and on one occasion he asked me to look through a microscope and describe what i saw. this i did, and believe now that it was the marvellous currents of protoplasm in some vegetable cell. i then asked him what i had seen; but he answered me, "that is my little secret." he was capable of the most generous actions. when old, much out of health, and quite unfit for any exertion, he daily visited (as hooker told me) an old man-servant, who lived at a distance (and whom he supported), and read aloud to him. this is enough to make up for any degree of scientific penuriousness or jealousy. i may here mention a few other eminent men, whom i have occasionally seen, but i have little to say about them worth saying. i felt a high reverence for sir j. herschel, and was delighted to dine with him at his charming house at the cape of good hope, and afterwards at his london house. i saw him, also, on a few other occasions. he never talked much, but every word which he uttered was worth listening to. i once met at breakfast at sir r. murchison's house the illustrious humboldt, who honoured me by expressing a wish to see me. i was a little disappointed with the great man, but my anticipations probably were too high. i can remember nothing distinctly about our interview, except that humboldt was very cheerful and talked much. --reminds me of buckle whom i once met at hensleigh wedgwood's. i was very glad to learn from him his system of collecting facts. he told me that he bought all the books which he read, and made a full index, to each, of the facts which he thought might prove serviceable to him, and that he could always remember in what book he had read anything, for his memory was wonderful. i asked him how at first he could judge what facts would be serviceable, and he answered that he did not know, but that a sort of instinct guided him. from this habit of making indices, he was enabled to give the astonishing number of references on all sorts of subjects, which may be found in his 'history of civilisation.' this book i thought most interesting, and read it twice, but i doubt whether his generalisations are worth anything. buckle was a great talker, and i listened to him saying hardly a word, nor indeed could i have done so for he left no gaps. when mrs. farrer began to sing, i jumped up and said that i must listen to her; after i had moved away he turned around to a friend and said (as was overheard by my brother), "well, mr. darwin's books are much better than his conversation." of other great literary men, i once met sydney smith at dean milman's house. there was something inexplicably amusing in every word which he uttered. perhaps this was partly due to the expectation of being amused. he was talking about lady cork, who was then extremely old. this was the lady who, as he said, was once so much affected by one of his charity sermons, that she _borrowed_ a guinea from a friend to put in the plate. he now said "it is generally believed that my dear old friend lady cork has been overlooked," and he said this in such a manner that no one could for a moment doubt that he meant that his dear old friend had been overlooked by the devil. how he managed to express this i know not. i likewise once met macaulay at lord stanhope's (the historian's) house, and as there was only one other man at dinner, i had a grand opportunity of hearing him converse, and he was very agreeable. he did not talk at all too much; nor indeed could such a man talk too much, as long as he allowed others to turn the stream of his conversation, and this he did allow. lord stanhope once gave me a curious little proof of the accuracy and fulness of macaulay's memory: many historians used often to meet at lord stanhope's house, and in discussing various subjects they would sometimes differ from macaulay, and formerly they often referred to some book to see who was right; but latterly, as lord stanhope noticed, no historian ever took this trouble, and whatever macaulay said was final. on another occasion i met at lord stanhope's house, one of his parties of historians and other literary men, and amongst them were motley and grote. after luncheon i walked about chevening park for nearly an hour with grote, and was much interested by his conversation and pleased by the simplicity and absence of all pretension in his manners. long ago i dined occasionally with the old earl, the father of the historian; he was a strange man, but what little i knew of him i liked much. he was frank, genial, and pleasant. he had strongly marked features, with a brown complexion, and his clothes, when i saw him, were all brown. he seemed to believe in everything which was to others utterly incredible. he said one day to me, "why don't you give up your fiddle-faddle of geology and zoology, and turn to the occult sciences!" the historian, then lord mahon, seemed shocked at such a speech to me, and his charming wife much amused. the last man whom i will mention is carlyle, seen by me several times at my brother's house, and two or three times at my own house. his talk was very racy and interesting, just like his writings, but he sometimes went on too long on the same subject. i remember a funny dinner at my brother's, where, amongst a few others, were babbage and lyell, both of whom liked to talk. carlyle, however, silenced every one by haranguing during the whole dinner on the advantages of silence. after dinner babbage, in his grimmest manner, thanked carlyle for his very interesting lecture on silence. carlyle sneered at almost every one: one day in my house he called grote's 'history' "a fetid quagmire, with nothing spiritual about it." i always thought, until his 'reminiscences' appeared, that his sneers were partly jokes, but this now seems rather doubtful. his expression was that of a depressed, almost despondent yet benevolent man; and it is notorious how heartily he laughed. i believe that his benevolence was real, though stained by not a little jealousy. no one can doubt about his extraordinary power of drawing pictures of things and men--far more vivid, as it appears to me, than any drawn by macaulay. whether his pictures of men were true ones is another question. he has been all-powerful in impressing some grand moral truths on the minds of men. on the other hand, his views about slavery were revolting. in his eyes might was right. his mind seemed to me a very narrow one; even if all branches of science, which he despised, are excluded. it is astonishing to me that kingsley should have spoken of him as a man well fitted to advance science. he laughed to scorn the idea that a mathematician, such as whewell, could judge, as i maintained he could, of goethe's views on light. he thought it a most ridiculous thing that any one should care whether a glacier moved a little quicker or a little slower, or moved at all. as far as i could judge, i never met a man with a mind so ill adapted for scientific research. whilst living in london, i attended as regularly as i could the meetings of several scientific societies, and acted as secretary to the geological society. but such attendance, and ordinary society, suited my health so badly that we resolved to live in the country, which we both preferred and have never repented of. residence at down from september 14, 1842, to the present time, 1876. after several fruitless searches in surrey and elsewhere, we found this house and purchased it. i was pleased with the diversified appearance of vegetation proper to a chalk district, and so unlike what i had been accustomed to in the midland counties; and still more pleased with the extreme quietness and rusticity of the place. it is not, however, quite so retired a place as a writer in a german periodical makes it, who says that my house can be approached only by a mule-track! our fixing ourselves here has answered admirably in one way, which we did not anticipate, namely, by being very convenient for frequent visits from our children. few persons can have lived a more retired life than we have done. besides short visits to the houses of relations, and occasionally to the seaside or elsewhere, we have gone nowhere. during the first part of our residence we went a little into society, and received a few friends here; but my health almost always suffered from the excitement, violent shivering and vomiting attacks being thus brought on. i have therefore been compelled for many years to give up all dinner-parties; and this has been somewhat of a deprivation to me, as such parties always put me into high spirits. from the same cause i have been able to invite here very few scientific acquaintances. my chief enjoyment and sole employment throughout life has been scientific work; and the excitement from such work makes me for the time forget, or drives quite away, my daily discomfort. i have therefore nothing to record during the rest of my life, except the publication of my several books. perhaps a few details how they arose may be worth giving. my several publications. in the early part of 1844, my observations on the volcanic islands visited during the voyage of the "beagle" were published. in 1845, i took much pains in correcting a new edition of my 'journal of researches,' which was originally published in 1839 as part of fitz-roy's work. the success of this, my first literary child, always tickles my vanity more than that of any of my other books. even to this day it sells steadily in england and the united states, and has been translated for the second time into german, and into french and other languages. this success of a book of travels, especially of a scientific one, so many years after its first publication, is surprising. ten thousand copies have been sold in england of the second edition. in 1846 my 'geological observations on south america' were published. i record in a little diary, which i have always kept, that my three geological books ('coral reefs' included) consumed four and a half years' steady work; "and now it is ten years since my return to england. how much time have i lost by illness?" i have nothing to say about these three books except that to my surprise new editions have lately been called for. ('geological observations,' 2nd edit.1876. 'coral reefs,' 2nd edit. 1874.) in october, 1846, i began to work on 'cirripedia.' when on the coast of chile, i found a most curious form, which burrowed into the shells of concholepas, and which differed so much from all other cirripedes that i had to form a new sub-order for its sole reception. lately an allied burrowing genus has been found on the shores of portugal. to understand the structure of my new cirripede i had to examine and dissect many of the common forms; and this gradually led me on to take up the whole group. i worked steadily on this subject for the next eight years, and ultimately published two thick volumes (published by the ray society.), describing all the known living species, and two thin quartos on the extinct species. i do not doubt that sir e. lytton bulwer had me in his mind when he introduced in one of his novels a professor long, who had written two huge volumes on limpets. although i was employed during eight years on this work, yet i record in my diary that about two years out of this time was lost by illness. on this account i went in 1848 for some months to malvern for hydropathic treatment, which did me much good, so that on my return home i was able to resume work. so much was i out of health that when my dear father died on november 13th, 1848, i was unable to attend his funeral or to act as one of his executors. my work on the cirripedia possesses, i think, considerable value, as besides describing several new and remarkable forms, i made out the homologies of the various parts--i discovered the cementing apparatus, though i blundered dreadfully about the cement glands--and lastly i proved the existence in certain genera of minute males complemental to and parasitic on the hermaphrodites. this latter discovery has at last been fully confirmed; though at one time a german writer was pleased to attribute the whole account to my fertile imagination. the cirripedes form a highly varying and difficult group of species to class; and my work was of considerable use to me, when i had to discuss in the 'origin of species' the principles of a natural classification. nevertheless, i doubt whether the work was worth the consumption of so much time. from september 1854 i devoted my whole time to arranging my huge pile of notes, to observing, and to experimenting in relation to the transmutation of species. during the voyage of the "beagle" i had been deeply impressed by discovering in the pampean formation great fossil animals covered with armour like that on the existing armadillos; secondly, by the manner in which closely allied animals replace one another in proceeding southwards over the continent; and thirdly, by the south american character of most of the productions of the galapagos archipelago, and more especially by the manner in which they differ slightly on each island of the group; none of the islands appearing to be very ancient in a geological sense. it was evident that such facts as these, as well as many others, could only be explained on the supposition that species gradually become modified; and the subject haunted me. but it was equally evident that neither the action of the surrounding conditions, nor the will of the organisms (especially in the case of plants) could account for the innumerable cases in which organisms of every kind are beautifully adapted to their habits of life--for instance, a woodpecker or a tree-frog to climb trees, or a seed for dispersal by hooks or plumes. i had always been much struck by such adaptations, and until these could be explained it seemed to me almost useless to endeavour to prove by indirect evidence that species have been modified. after my return to england it appeared to me that by following the example of lyell in geology, and by collecting all facts which bore in any way on the variation of animals and plants under domestication and nature, some light might perhaps be thrown on the whole subject. my first note-book was opened in july 1837. i worked on true baconian principles, and without any theory collected facts on a wholesale scale, more especially with respect to domesticated productions, by printed enquiries, by conversation with skilful breeders and gardeners, and by extensive reading. when i see the list of books of all kinds which i read and abstracted, including whole series of journals and transactions, i am surprised at my industry. i soon perceived that selection was the keystone of man's success in making useful races of animals and plants. but how selection could be applied to organisms living in a state of nature remained for some time a mystery to me. in october 1838, that is, fifteen months after i had begun my systematic enquiry, i happened to read for amusement 'malthus on population,' and being well prepared to appreciate the struggle for existence which everywhere goes on from long-continued observation of the habits of animals and plants, it at once struck me that under these circumstances favourable variations would tend to be preserved, and unfavourable ones to be destroyed. the result of this would be the formation of new species. here then i had at last got a theory by which to work; but i was so anxious to avoid prejudice, that i determined not for some time to write even the briefest sketch of it. in june 1842 i first allowed myself the satisfaction of writing a very brief abstract of my theory in pencil in 35 pages; and this was enlarged during the summer of 1844 into one of 230 pages, which i had fairly copied out and still possess. but at that time i overlooked one problem of great importance; and it is astonishing to me, except on the principle of columbus and his egg, how i could have overlooked it and its solution. this problem is the tendency in organic beings descended from the same stock to diverge in character as they become modified. that they have diverged greatly is obvious from the manner in which species of all kinds can be classed under genera, genera under families, families under sub-orders and so forth; and i can remember the very spot in the road, whilst in my carriage, when to my joy the solution occurred to me; and this was long after i had come to down. the solution, as i believe, is that the modified offspring of all dominant and increasing forms tend to become adapted to many and highly diversified places in the economy of nature. early in 1856 lyell advised me to write out my views pretty fully, and i began at once to do so on a scale three or four times as extensive as that which was afterwards followed in my 'origin of species;' yet it was only an abstract of the materials which i had collected, and i got through about half the work on this scale. but my plans were overthrown, for early in the summer of 1858 mr. wallace, who was then in the malay archipelago, sent me an essay "on the tendency of varieties to depart indefinitely from the original type;" and this essay contained exactly the same theory as mine. mr. wallace expressed the wish that if i thought well of his essay, i should sent it to lyell for perusal. the circumstances under which i consented at the request of lyell and hooker to allow of an abstract from my ms., together with a letter to asa gray, dated september 5, 1857, to be published at the same time with wallace's essay, are given in the 'journal of the proceedings of the linnean society,' 1858, page 45. i was at first very unwilling to consent, as i thought mr. wallace might consider my doing so unjustifiable, for i did not then know how generous and noble was his disposition. the extract from my ms. and the letter to asa gray had neither been intended for publication, and were badly written. mr. wallace's essay, on the other hand, was admirably expressed and quite clear. nevertheless, our joint productions excited very little attention, and the only published notice of them which i can remember was by professor haughton of dublin, whose verdict was that all that was new in them was false, and what was true was old. this shows how necessary it is that any new view should be explained at considerable length in order to arouse public attention. in september 1858 i set to work by the strong advice of lyell and hooker to prepare a volume on the transmutation of species, but was often interrupted by ill-health, and short visits to dr. lane's delightful hydropathic establishment at moor park. i abstracted the ms. begun on a much larger scale in 1856, and completed the volume on the same reduced scale. it cost me thirteen months and ten days' hard labour. it was published under the title of the 'origin of species,' in november 1859. though considerably added to and corrected in the later editions, it has remained substantially the same book. it is no doubt the chief work of my life. it was from the first highly successful. the first small edition of 1250 copies was sold on the day of publication, and a second edition of 3000 copies soon afterwards. sixteen thousand copies have now (1876) been sold in england; and considering how stiff a book it is, this is a large sale. it has been translated into almost every european tongue, even into such languages as spanish, bohemian, polish, and russian. it has also, according to miss bird, been translated into japanese (miss bird is mistaken, as i learn from prof. mitsukuri.--f.d.), and is there much studied. even an essay in hebrew has appeared on it, showing that the theory is contained in the old testament! the reviews were very numerous; for some time i collected all that appeared on the 'origin' and on my related books, and these amount (excluding newspaper reviews) to 265; but after a time i gave up the attempt in despair. many separate essays and books on the subject have appeared; and in germany a catalogue or bibliography on "darwinismus" has appeared every year or two. the success of the 'origin' may, i think, be attributed in large part to my having long before written two condensed sketches, and to my having finally abstracted a much larger manuscript, which was itself an abstract. by this means i was enabled to select the more striking facts and conclusions. i had, also, during many years followed a golden rule, namely, that whenever a published fact, a new observation or thought came across me, which was opposed to my general results, to make a memorandum of it without fail and at once; for i had found by experience that such facts and thoughts were far more apt to escape from the memory than favourable ones. owing to this habit, very few objections were raised against my views which i had not at least noticed and attempted to answer. it has sometimes been said that the success of the 'origin' proved "that the subject was in the air," or "that men's minds were prepared for it." i do not think that this is strictly true, for i occasionally sounded not a few naturalists, and never happened to come across a single one who seemed to doubt about the permanence of species. even lyell and hooker, though they would listen with interest to me, never seemed to agree. i tried once or twice to explain to able men what i meant by natural selection, but signally failed. what i believe was strictly true is that innumerable well-observed facts were stored in the minds of naturalists ready to take their proper places as soon as any theory which would receive them was sufficiently explained. another element in the success of the book was its moderate size; and this i owe to the appearance of mr. wallace's essay; had i published on the scale in which i began to write in 1856, the book would have been four or five times as large as the 'origin,' and very few would have had the patience to read it. i gained much by my delay in publishing from about 1839, when the theory was clearly conceived, to 1859; and i lost nothing by it, for i cared very little whether men attributed most originality to me or wallace; and his essay no doubt aided in the reception of the theory. i was forestalled in only one important point, which my vanity has always made me regret, namely, the explanation by means of the glacial period of the presence of the same species of plants and of some few animals on distant mountain summits and in the arctic regions. this view pleased me so much that i wrote it out in extenso, and i believe that it was read by hooker some years before e. forbes published his celebrated memoir ('geolog. survey mem.,' 1846.) on the subject. in the very few points in which we differed, i still think that i was in the right. i have never, of course, alluded in print to my having independently worked out this view. hardly any point gave me so much satisfaction when i was at work on the 'origin,' as the explanation of the wide difference in many classes between the embryo and the adult animal, and of the close resemblance of the embryos within the same class. no notice of this point was taken, as far as i remember, in the early reviews of the 'origin,' and i recollect expressing my surprise on this head in a letter to asa gray. within late years several reviewers have given the whole credit to fritz muller and hackel, who undoubtedly have worked it out much more fully, and in some respects more correctly than i did. i had materials for a whole chapter on the subject, and i ought to have made the discussion longer; for it is clear that i failed to impress my readers; and he who succeeds in doing so deserves, in my opinion, all the credit. this leads me to remark that i have almost always been treated honestly by my reviewers, passing over those without scientific knowledge as not worthy of notice. my views have often been grossly misrepresented, bitterly opposed and ridiculed, but this has been generally done, as i believe, in good faith. on the whole i do not doubt that my works have been over and over again greatly overpraised. i rejoice that i have avoided controversies, and this i owe to lyell, who many years ago, in reference to my geological works, strongly advised me never to get entangled in a controversy, as it rarely did any good and caused a miserable loss of time and temper. whenever i have found out that i have blundered, or that my work has been imperfect, and when i have been contemptuously criticised, and even when i have been overpraised, so that i have felt mortified, it has been my greatest comfort to say hundreds of times to myself that "i have worked as hard and as well as i could, and no man can do more than this." i remember when in good success bay, in tierra del fuego, thinking (and, i believe, that i wrote home to the effect) that i could not employ my life better than in adding a little to natural science. this i have done to the best of my abilities, and critics may say what they like, but they cannot destroy this conviction. during the two last months of 1859 i was fully occupied in preparing a second edition of the 'origin,' and by an enormous correspondence. on january 1st, 1860, i began arranging my notes for my work on the 'variation of animals and plants under domestication;' but it was not published until the beginning of 1868; the delay having been caused partly by frequent illnesses, one of which lasted seven months, and partly by being tempted to publish on other subjects which at the time interested me more. on may 15th, 1862, my little book on the 'fertilisation of orchids,' which cost me ten months' work, was published: most of the facts had been slowly accumulated during several previous years. during the summer of 1839, and, i believe, during the previous summer, i was led to attend to the cross-fertilisation of flowers by the aid of insects, from having come to the conclusion in my speculations on the origin of species, that crossing played an important part in keeping specific forms constant. i attended to the subject more or less during every subsequent summer; and my interest in it was greatly enhanced by having procured and read in november 1841, through the advice of robert brown, a copy of c.k. sprengel's wonderful book, 'das entdeckte geheimniss der natur.' for some years before 1862 i had specially attended to the fertilisation of our british orchids; and it seemed to me the best plan to prepare as complete a treatise on this group of plants as well as i could, rather than to utilise the great mass of matter which i had slowly collected with respect to other plants. my resolve proved a wise one; for since the appearance of my book, a surprising number of papers and separate works on the fertilisation of all kinds of flowers have appeared: and these are far better done than i could possibly have effected. the merits of poor old sprengel, so long overlooked, are now fully recognised many years after his death. during the same year i published in the 'journal of the linnean society' a paper "on the two forms, or dimorphic condition of primula," and during the next five years, five other papers on dimorphic and trimorphic plants. i do not think anything in my scientific life has given me so much satisfaction as making out the meaning of the structure of these plants. i had noticed in 1838 or 1839 the dimorphism of linum flavum, and had at first thought that it was merely a case of unmeaning variability. but on examining the common species of primula i found that the two forms were much too regular and constant to be thus viewed. i therefore became almost convinced that the common cowslip and primrose were on the high road to become dioecious;--that the short pistil in the one form, and the short stamens in the other form were tending towards abortion. the plants were therefore subjected under this point of view to trial; but as soon as the flowers with short pistils fertilised with pollen from the short stamens, were found to yield more seeds than any other of the four possible unions, the abortion-theory was knocked on the head. after some additional experiment, it became evident that the two forms, though both were perfect hermaphrodites, bore almost the same relation to one another as do the two sexes of an ordinary animal. with lythrum we have the still more wonderful case of three forms standing in a similar relation to one another. i afterwards found that the offspring from the union of two plants belonging to the same forms presented a close and curious analogy with hybrids from the union of two distinct species. in the autumn of 1864 i finished a long paper on 'climbing plants,' and sent it to the linnean society. the writing of this paper cost me four months; but i was so unwell when i received the proof-sheets that i was forced to leave them very badly and often obscurely expressed. the paper was little noticed, but when in 1875 it was corrected and published as a separate book it sold well. i was led to take up this subject by reading a short paper by asa gray, published in 1858. he sent me seeds, and on raising some plants i was so much fascinated and perplexed by the revolving movements of the tendrils and stems, which movements are really very simple, though appearing at first sight very complex, that i procured various other kinds of climbing plants, and studied the whole subject. i was all the more attracted to it, from not being at all satisfied with the explanation which henslow gave us in his lectures, about twining plants, namely, that they had a natural tendency to grow up in a spire. this explanation proved quite erroneous. some of the adaptations displayed by climbing plants are as beautiful as those of orchids for ensuring cross-fertilisation. my 'variation of animals and plants under domestication' was begun, as already stated, in the beginning of 1860, but was not published until the beginning of 1868. it was a big book, and cost me four years and two months' hard labour. it gives all my observations and an immense number of facts collected from various sources, about our domestic productions. in the second volume the causes and laws of variation, inheritance, etc., are discussed as far as our present state of knowledge permits. towards the end of the work i give my well-abused hypothesis of pangenesis. an unverified hypothesis is of little or no value; but if anyone should hereafter be led to make observations by which some such hypothesis could be established, i shall have done good service, as an astonishing number of isolated facts can be thus connected together and rendered intelligible. in 1875 a second and largely corrected edition, which cost me a good deal of labour, was brought out. my 'descent of man' was published in february, 1871. as soon as i had become, in the year 1837 or 1838, convinced that species were mutable productions, i could not avoid the belief that man must come under the same law. accordingly i collected notes on the subject for my own satisfaction, and not for a long time with any intention of publishing. although in the 'origin of species' the derivation of any particular species is never discussed, yet i thought it best, in order that no honourable man should accuse me of concealing my views, to add that by the work "light would be thrown on the origin of man and his history." it would have been useless and injurious to the success of the book to have paraded, without giving any evidence, my conviction with respect to his origin. but when i found that many naturalists fully accepted the doctrine of the evolution of species, it seemed to me advisable to work up such notes as i possessed, and to publish a special treatise on the origin of man. i was the more glad to do so, as it gave me an opportunity of fully discussing sexual selection--a subject which had always greatly interested me. this subject, and that of the variation of our domestic productions, together with the causes and laws of variation, inheritance, and the intercrossing of plants, are the sole subjects which i have been able to write about in full, so as to use all the materials which i have collected. the 'descent of man' took me three years to write, but then as usual some of this time was lost by ill health, and some was consumed by preparing new editions and other minor works. a second and largely corrected edition of the 'descent' appeared in 1874. my book on the 'expression of the emotions in men and animals' was published in the autumn of 1872. i had intended to give only a chapter on the subject in the 'descent of man,' but as soon as i began to put my notes together, i saw that it would require a separate treatise. my first child was born on december 27th, 1839, and i at once commenced to make notes on the first dawn of the various expressions which he exhibited, for i felt convinced, even at this early period, that the most complex and fine shades of expression must all have had a gradual and natural origin. during the summer of the following year, 1840, i read sir c. bell's admirable work on expression, and this greatly increased the interest which i felt in the subject, though i could not at all agree with his belief that various muscles had been specially created for the sake of expression. from this time forward i occasionally attended to the subject, both with respect to man and our domesticated animals. my book sold largely; 5267 copies having been disposed of on the day of publication. in the summer of 1860 i was idling and resting near hartfield, where two species of drosera abound; and i noticed that numerous insects had been entrapped by the leaves. i carried home some plants, and on giving them insects saw the movements of the tentacles, and this made me think it probable that the insects were caught for some special purpose. fortunately a crucial test occurred to me, that of placing a large number of leaves in various nitrogenous and non-nitrogenous fluids of equal density; and as soon as i found that the former alone excited energetic movements, it was obvious that here was a fine new field for investigation. during subsequent years, whenever i had leisure, i pursued my experiments, and my book on 'insectivorous plants' was published in july 1875--that is, sixteen years after my first observations. the delay in this case, as with all my other books, has been a great advantage to me; for a man after a long interval can criticise his own work, almost as well as if it were that of another person. the fact that a plant should secrete, when properly excited, a fluid containing an acid and ferment, closely analogous to the digestive fluid of an animal, was certainly a remarkable discovery. during this autumn of 1876 i shall publish on the 'effects of cross and self-fertilisation in the vegetable kingdom.' this book will form a complement to that on the 'fertilisation of orchids,' in which i showed how perfect were the means for cross-fertilisation, and here i shall show how important are the results. i was led to make, during eleven years, the numerous experiments recorded in this volume, by a mere accidental observation; and indeed it required the accident to be repeated before my attention was thoroughly aroused to the remarkable fact that seedlings of self-fertilised parentage are inferior, even in the first generation, in height and vigour to seedlings of cross-fertilised parentage. i hope also to republish a revised edition of my book on orchids, and hereafter my papers on dimorphic and trimorphic plants, together with some additional observations on allied points which i never have had time to arrange. my strength will then probably be exhausted, and i shall be ready to exclaim "nunc dimittis." written may 1st, 1881. 'the effects of cross and self-fertilisation' was published in the autumn of 1876; and the results there arrived at explain, as i believe, the endless and wonderful contrivances for the transportal of pollen from one plant to another of the same species. i now believe, however, chiefly from the observations of hermann muller, that i ought to have insisted more strongly than i did on the many adaptations for self-fertilisation; though i was well aware of many such adaptations. a much enlarged edition of my 'fertilisation of orchids' was published in 1877. in this same year 'the different forms of flowers, etc.,' appeared, and in 1880 a second edition. this book consists chiefly of the several papers on heterostyled flowers originally published by the linnean society, corrected, with much new matter added, together with observations on some other cases in which the same plant bears two kinds of flowers. as before remarked, no little discovery of mine ever gave me so much pleasure as the making out the meaning of heterostyled flowers. the results of crossing such flowers in an illegitimate manner, i believe to be very important, as bearing on the sterility of hybrids; although these results have been noticed by only a few persons. in 1879, i had a translation of dr. ernst krause's 'life of erasmus darwin' published, and i added a sketch of his character and habits from material in my possession. many persons have been much interested by this little life, and i am surprised that only 800 or 900 copies were sold. in 1880 i published, with [my son] frank's assistance, our 'power of movement in plants.' this was a tough piece of work. the book bears somewhat the same relation to my little book on 'climbing plants,' which 'cross-fertilisation' did to the 'fertilisation of orchids;' for in accordance with the principle of evolution it was impossible to account for climbing plants having been developed in so many widely different groups unless all kinds of plants possess some slight power of movement of an analogous kind. this i proved to be the case; and i was further led to a rather wide generalisation, viz. that the great and important classes of movements, excited by light, the attraction of gravity, etc., are all modified forms of the fundamental movement of circumnutation. it has always pleased me to exalt plants in the scale of organised beings; and i therefore felt an especial pleasure in showing how many and what admirably well adapted movements the tip of a root possesses. i have now (may 1, 1881) sent to the printers the ms. of a little book on 'the formation of vegetable mould, through the action of worms.' this is a subject of but small importance; and i know not whether it will interest any readers (between november 1881 and february 1884, 8500 copies have been sold.), but it has interested me. it is the completion of a short paper read before the geological society more than forty years ago, and has revived old geological thoughts. i have now mentioned all the books which i have published, and these have been the milestones in my life, so that little remains to be said. i am not conscious of any change in my mind during the last thirty years, excepting in one point presently to be mentioned; nor, indeed, could any change have been expected unless one of general deterioration. but my father lived to his eighty-third year with his mind as lively as ever it was, and all his faculties undimmed; and i hope that i may die before my mind fails to a sensible extent. i think that i have become a little more skilful in guessing right explanations and in devising experimental tests; but this may probably be the result of mere practice, and of a larger store of knowledge. i have as much difficulty as ever in expressing myself clearly and concisely; and this difficulty has caused me a very great loss of time; but it has had the compensating advantage of forcing me to think long and intently about every sentence, and thus i have been led to see errors in reasoning and in my own observations or those of others. there seems to be a sort of fatality in my mind leading me to put at first my statement or proposition in a wrong or awkward form. formerly i used to think about my sentences before writing them down; but for several years i have found that it saves time to scribble in a vile hand whole pages as quickly as i possibly can, contracting half the words; and then correct deliberately. sentences thus scribbled down are often better ones than i could have written deliberately. having said thus much about my manner of writing, i will add that with my large books i spend a good deal of time over the general arrangement of the matter. i first make the rudest outline in two or three pages, and then a larger one in several pages, a few words or one word standing for a whole discussion or series of facts. each one of these headings is again enlarged and often transferred before i begin to write in extenso. as in several of my books facts observed by others have been very extensively used, and as i have always had several quite distinct subjects in hand at the same time, i may mention that i keep from thirty to forty large portfolios, in cabinets with labelled shelves, into which i can at once put a detached reference or memorandum. i have bought many books, and at their ends i make an index of all the facts that concern my work; or, if the book is not my own, write out a separate abstract, and of such abstracts i have a large drawer full. before beginning on any subject i look to all the short indexes and make a general and classified index, and by taking the one or more proper portfolios i have all the information collected during my life ready for use. i have said that in one respect my mind has changed during the last twenty or thirty years. up to the age of thirty, or beyond it, poetry of many kinds, such as the works of milton, gray, byron, wordsworth, coleridge, and shelley, gave me great pleasure, and even as a schoolboy i took intense delight in shakespeare, especially in the historical plays. i have also said that formerly pictures gave me considerable, and music very great delight. but now for many years i cannot endure to read a line of poetry: i have tried lately to read shakespeare, and found it so intolerably dull that it nauseated me. i have also almost lost my taste for pictures or music. music generally sets me thinking too energetically on what i have been at work on, instead of giving me pleasure. i retain some taste for fine scenery, but it does not cause me the exquisite delight which it formerly did. on the other hand, novels which are works of the imagination, though not of a very high order, have been for years a wonderful relief and pleasure to me, and i often bless all novelists. a surprising number have been read aloud to me, and i like all if moderately good, and if they do not end unhappily--against which a law ought to be passed. a novel, according to my taste, does not come into the first class unless it contains some person whom one can thoroughly love, and if a pretty woman all the better. this curious and lamentable loss of the higher aesthetic tastes is all the odder, as books on history, biographies, and travels (independently of any scientific facts which they may contain), and essays on all sorts of subjects interest me as much as ever they did. my mind seems to have become a kind of machine for grinding general laws out of large collections of facts, but why this should have caused the atrophy of that part of the brain alone, on which the higher tastes depend, i cannot conceive. a man with a mind more highly organised or better constituted than mine, would not, i suppose, have thus suffered; and if i had to live my life again, i would have made a rule to read some poetry and listen to some music at least once every week; for perhaps the parts of my brain now atrophied would thus have been kept active through use. the loss of these tastes is a loss of happiness, and may possibly be injurious to the intellect, and more probably to the moral character, by enfeebling the emotional part of our nature. my books have sold largely in england, have been translated into many languages, and passed through several editions in foreign countries. i have heard it said that the success of a work abroad is the best test of its enduring value. i doubt whether this is at all trustworthy; but judged by this standard my name ought to last for a few years. therefore it may be worth while to try to analyse the mental qualities and the conditions on which my success has depended; though i am aware that no man can do this correctly. i have no great quickness of apprehension or wit which is so remarkable in some clever men, for instance, huxley. i am therefore a poor critic: a paper or book, when first read, generally excites my admiration, and it is only after considerable reflection that i perceive the weak points. my power to follow a long and purely abstract train of thought is very limited; and therefore i could never have succeeded with metaphysics or mathematics. my memory is extensive, yet hazy: it suffices to make me cautious by vaguely telling me that i have observed or read something opposed to the conclusion which i am drawing, or on the other hand in favour of it; and after a time i can generally recollect where to search for my authority. so poor in one sense is my memory, that i have never been able to remember for more than a few days a single date or a line of poetry. some of my critics have said, "oh, he is a good observer, but he has no power of reasoning!" i do not think that this can be true, for the 'origin of species' is one long argument from the beginning to the end, and it has convinced not a few able men. no one could have written it without having some power of reasoning. i have a fair share of invention, and of common sense or judgment, such as every fairly successful lawyer or doctor must have, but not, i believe, in any higher degree. on the favourable side of the balance, i think that i am superior to the common run of men in noticing things which easily escape attention, and in observing them carefully. my industry has been nearly as great as it could have been in the observation and collection of facts. what is far more important, my love of natural science has been steady and ardent. this pure love has, however, been much aided by the ambition to be esteemed by my fellow naturalists. from my early youth i have had the strongest desire to understand or explain whatever i observed,--that is, to group all facts under some general laws. these causes combined have given me the patience to reflect or ponder for any number of years over any unexplained problem. as far as i can judge, i am not apt to follow blindly the lead of other men. i have steadily endeavoured to keep my mind free so as to give up any hypothesis, however much beloved (and i cannot resist forming one on every subject), as soon as facts are shown to be opposed to it. indeed, i have had no choice but to act in this manner, for with the exception of the coral reefs, i cannot remember a single first-formed hypothesis which had not after a time to be given up or greatly modified. this has naturally led me to distrust greatly deductive reasoning in the mixed sciences. on the other hand, i am not very sceptical,--a frame of mind which i believe to be injurious to the progress of science. a good deal of scepticism in a scientific man is advisable to avoid much loss of time, but i have met with not a few men, who, i feel sure, have often thus been deterred from experiment or observations, which would have proved directly or indirectly serviceable. in illustration, i will give the oddest case which i have known. a gentleman (who, as i afterwards heard, is a good local botanist) wrote to me from the eastern counties that the seed or beans of the common field-bean had this year everywhere grown on the wrong side of the pod. i wrote back, asking for further information, as i did not understand what was meant; but i did not receive any answer for a very long time. i then saw in two newspapers, one published in kent and the other in yorkshire, paragraphs stating that it was a most remarkable fact that "the beans this year had all grown on the wrong side." so i thought there must be some foundation for so general a statement. accordingly, i went to my gardener, an old kentish man, and asked him whether he had heard anything about it, and he answered, "oh, no, sir, it must be a mistake, for the beans grow on the wrong side only on leap-year, and this is not leap-year." i then asked him how they grew in common years and how on leap-years, but soon found that he knew absolutely nothing of how they grew at any time, but he stuck to his belief. after a time i heard from my first informant, who, with many apologies, said that he should not have written to me had he not heard the statement from several intelligent farmers; but that he had since spoken again to every one of them, and not one knew in the least what he had himself meant. so that here a belief--if indeed a statement with no definite idea attached to it can be called a belief--had spread over almost the whole of england without any vestige of evidence. i have known in the course of my life only three intentionally falsified statements, and one of these may have been a hoax (and there have been several scientific hoaxes) which, however, took in an american agricultural journal. it related to the formation in holland of a new breed of oxen by the crossing of distinct species of bos (some of which i happen to know are sterile together), and the author had the impudence to state that he had corresponded with me, and that i had been deeply impressed with the importance of his result. the article was sent to me by the editor of an english agricultural journal, asking for my opinion before republishing it. a second case was an account of several varieties, raised by the author from several species of primula, which had spontaneously yielded a full complement of seed, although the parent plants had been carefully protected from the access of insects. this account was published before i had discovered the meaning of heterostylism, and the whole statement must have been fraudulent, or there was neglect in excluding insects so gross as to be scarcely credible. the third case was more curious: mr. huth published in his book on 'consanguineous marriage' some long extracts from a belgian author, who stated that he had interbred rabbits in the closest manner for very many generations, without the least injurious effects. the account was published in a most respectable journal, that of the royal society of belgium; but i could not avoid feeling doubts--i hardly know why, except that there were no accidents of any kind, and my experience in breeding animals made me think this very improbable. so with much hesitation i wrote to professor van beneden, asking him whether the author was a trustworthy man. i soon heard in answer that the society had been greatly shocked by discovering that the whole account was a fraud. (the falseness of the published statements on which mr. huth relied has been pointed out by himself in a slip inserted in all the copies of his book which then remained unsold.) the writer had been publicly challenged in the journal to say where he had resided and kept his large stock of rabbits while carrying on his experiments, which must have consumed several years, and no answer could be extracted from him. my habits are methodical, and this has been of not a little use for my particular line of work. lastly, i have had ample leisure from not having to earn my own bread. even ill-health, though it has annihilated several years of my life, has saved me from the distractions of society and amusement. therefore my success as a man of science, whatever this may have amounted to, has been determined, as far as i can judge, by complex and diversified mental qualities and conditions. of these, the most important have been--the love of science--unbounded patience in long reflecting over any subject--industry in observing and collecting facts--and a fair share of invention as well as of common sense. with such moderate abilities as i possess, it is truly surprising that i should have influenced to a considerable extent the belief of scientific men on some important points. 