Prof


ISJ 6: S3-S8, 2009                                       ISSN 1824-307X 
 
 

REVIEW 
 
Professor Giuseppe Reverberi and the ascidian school in Palermo 
 
F De Bernardi 
 
Department of Biology, University of Milan, Milan, Italy 
 
 

Accepted March 13, 2009 
 
Giuseppe Reverberi was born near Perugia on 

1901. After being ordained as a priest, he graduated 
in Theology in 1924 from The Pontificio Ateneo 
Lateranense. In the same year, he went to the 
University of Rome, where he took another degree 
in Natural Science in the lab directed by Federico 
Raffaele, working on amphibian and chick embryos, 
under the guidance of professor Pasquale Pasquini. 
After the degree, he became an assistant at the 
Zoological Institute where started his studies in the 
field of experimental embryology, carrying out 
researches on the chick embryo-eye, on the 
centrifugation of the amphibian egg and on the 
potentialities of the amphibian tail bud: these 
researches were then continued in Palermo by 
some of his collaborators. 

In 1930 he qualified to teach General 
Embryology and became Professor of Experimental 
Psychology and Biology at the Ateneo Lateranense. 
In 1939 he was appointed at the University of 
Perugia as director of the Zoological institute. In the 
meantime, he worked at the Zoological Station of 
Naples, a great attraction pole of international level 
for marine biology and a breeding ground of 
scientists. Here he became Director of the Biological 
Center of the National Council for Research and 
started to study the first stages of development of 
the ascidian embryos.  

In 1948, as a winner of a public competition, he 
was appointed as professor of Zoology at the 
University of Palermo, where he was Director of the 
Zoological institute and Professor of Biology at the 
Medical School. 

In 1957 he founded the magazine Acta 
Embryologiae et Morphologiae Experimentalis, a 
Latin title for an international journal published in 
English, the first in Italy with an international 
editorial board. It represented a person whose 
broad knowledge was not limited to biology, but also 
covered philosophy, literature and theology. His 
researches, together with those carried out by the 
many research groups led by his collaborators were 
addressed essentially to developmental biology of 
several animals, overall marine invertebrates: annelids, 
___________________________________________________________________________ 

 
Corresponding author: 
Fiorenza De Bernardi 
Department of Biology 
University of Milan 
Via Celoria 26, 20133 Milan, Italy 
E-mail: fiorenza.debernardi@unimi.it 

mollusca (Dentalium) ctenophora, amphioxus and 
ascidians. In 1971 he published a fundamental 
textbook Experimental embryology of marine and 
fresh-water invertebrates (North Holland) which 
received a lot of quotations. 

For the above mentioned reasons, I wish to 
speak about the monumental scientific activity of 
professor Reverberi, which lasted more than 50 
years, and of his outstanding human personality. 
Unfortunately, I did not have the honour to be one of 
his pupils, but I can remember very well two 
meetings. 

The first one was in 1968, at the Zoological 
Station of Naples, during an Experimental 
Embryology course for young researchers: his tall 
figure, full of charisma, his availability to meet young 
people coming from different European countries for 
a dinner party. He was there with the teachers of the 
School, all the most outstanding embryologists of 
the 20th century: John Runnstrom, Sven Horstadius, 
Jean Brachet, Tryggve Gustafson, Gerhard Czihak. 
I was very impressed by the friendly terms between 
professor Reverberi and all those distinguished 
embryologists. It was a very important signal of his 
international reputation in a period (40 years ago) 
when not all the Italian Universities used to be so 
well-known abroad. 

I remember the meeting of the Italian 
Embryological Group in 1977, an atypical club born 
in 1952 from the idea of some Italian scientists on 
the model of the Institut International d’Embryologie 
(IIE). The founders were Pasquale Pasquini, Silvio 
Ranzi, Alberto Monroy, Alberto Stefanelli, Mario 
Benazzi and, obviously, Reverberi himself, who was 
a member of the IIE. During this meeting, professor 
Reverberi gave a lecture on the latest results and 
the perspectives of the ultrastructure and the 
cellular biochemistry of developing embryos, in 
which he compared and discussed the most recent 
results obtained in the Palermo lab and in many 
other labs all over the world . I was very impressed 
by the fervour of his speech about the 
communication between nucleus and cytoplasm, 
one of his favourite subjects. 

Ten years later, in 1987, I entered the Institute 
of Zoology in the historical place of via Archirafi 18: 
this building was still characterized by his strong 
personality, even if his illness kept him away for 
many years. In fact, most researchers were working 
on ascidians and this was the demonstration that a 
real School had been created there; a place where the 

 
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Fig. 1 Prof. Giuseppe Reverberi at work in his room at the Institute of Zoology of Palermo in 1965. 

 
 

same animal model was studied under manifold 
point of view. This fact impressed me very much as 
I was coming from the Zoological Institute of Milan, 
where the researches used to be more 
heterogeneous.  

It was then inevitable to be overwhelmed by the 
contagious enthusiasm of his first collaborator and 
outstanding successor, Giuseppina Ortolani, for the 
manipulation of the embryos and eggs of the 
ascidians: one day I told her the technical troubles 
encountered when highlighting some RNA markers 
in opaque Xenopus embryos, and she said to me:“I 
worked a lot with Xenopus eggs: my advice is to 
work with Phallusia, which has big, transparent and 
wonderful eggs. Try it and you’ll see!” So, I have 
been working for 20 years with ascidian embryos 
and I am feeling, even indirectly, an alumna of the 
famous ascidian school of Palermo! 

Reverberi’s scientific activity in Palermo mainly 
involved the experimental embryology field, but the 
development of ascidian eggs always gained first 
priority among his interests. In the following sections 
I will try to define the main research lines 
concerning the ascidian development. 

 
Development of egg fragments and isolated 
blastomeres  

 
When Reverberi started to work on the 

development of ascidians, the current information 
on such matter was that developed by Conklin, who 
wrote in the conclusion of his famous paper 
published in 1905: “The development of ascidians is 

a mosaic work because there are definitely localized 
organ-forming substances in the egg; in fact the 
mosaic is one of organ-forming substances rather 
than of cleavage cells. The study of ctenophores, 
nemertines, annelids, mollusks, ascidians and 
amphibians (the frog) shows that the same is 
probably true of all these forms and it suggests that 
the mosaic principle may apply to all animals.”  

It is interesting to follow the evolution during the 
time in which Reverberi formed his opinion about 
the mosaicism based on experimental results. 

In one of his first papers, in 1931, Reverberi 
describes the results obtained from the fertilization 
of egg fragments obtained by gentle crushing or by 
a small incision of the chorion. The fragments until 
1/22 collected by a needle tip developed “as a 
whole” and gave normal larvae. His conclusion was 
“The Ciona egg has to be classified among the 
regulative eggs” (Reverberi, 1931). 

1933: blastomeres separated at stages 2,4,8: 
the animal 4/8 developed blastulae; the vegetal 4/8 
developed also gastrulae. “The cleavage is strictly 
partial (=incomplete), even if some aspects could 
make suspect of a regulation” (Reverberi, 1933). 

1936: “The partial cleavage appears only from 
the two blastomere stage onwards…; before this 
stage in fertilized egg the cleavage is of total type” 
(Reverberi, 1936). 

In a frequently quoted paper, even if published 
only in Italian (Reverberi and Minganti, 1946), we 
can find some very beautiful drawings, much more 
explanatory than modern photos. Such drawings 
showed the results of the selective removal of two 

 
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blastomeres each time at 8-cell stage and the 
histological sections of the larvae obtained from the 
combination of the animal quartet with the two 
vegetal anterior blastomeres. This was the first 
paper unambiguously proving the existence of a 
“brain evocator” in the two vegetal anterior 
blastomeres and of a “ brain inhibitor” in vegetal 
posterior blastomeres. These figures became well 
known as reported in the book of Nori Satoh 
“Developmental biology of ascidians” (1994), a 
textbook widely diffused in the world of ascidian 
researchers. 

In another paper of the following year 
(Reverberi and Minganti, 1947), the systematic 
combinations of blastomeres were described and it 
was shown that vegetal anterior blastomeres do not 
“induce” any presumptive epidermis to become 
brain, but they only “evocate” the neural 
presumptive ectoderm to become brain.  

These works were continued and reconsidered 
with other collaborators in the following years. They 
used the knowledge obtained in the meantime by 
Ortolani about the cell-lineage of the single 
blastomeres until 64-cell stage and systematically 
removed the cells committed to give notochord or 
endoderm from stage 8 to 64. The single cells 
obtained were then transplanted under an isolated 
animal quartet. This great bulk of experiments, 
singularly evaluated, definitely showed that “The 
formation of the neural system in the ascidians is 
strictly directed by the same laws which Spemann 
discovered in the amphibians. Only slight 
differences are to be noticed between the inductive 
system in the amphibian and in the ascidians: in the 
amphibians, the inductor is chorda-mesoderm, in 
the ascidians it is (part of) the chorda-entoderm”. 
The observation that in the ascidians the inducing 
power of the chorda-endoderm was more restricted 
than in the amphibian led to support the idea of the 
“evocative” power instead of an “inducing” power, 
enclosed in a bright discussion among the 
embryologists at that time. These results were 
reported in another frequently quoted paper “The 
causal formation of the brain in the ascidian larva” 
(Reverberi et al., 1960). 

It is to be noted that this discussion is coming 
close to a solution only in recent years, after the 
genome sequencing and the knowledge of the 
sequences involved in determination of embryonic 
territories.  

 
Development of sense organs  

 
At the same time of the study on the induction 

of the nervous system and in the same papers was 
also studied the development of the principal sense 
organs: the otholith, the ocellus and the palps. A 
very elegant result was the cytochemical detection 
of the DOPA oxidase, the enzyme activating the 
melanin precursor, only after the induction process 
at neurula stage. Twenty years later, the problem of 
the sense organ development was resumed and in 
two papers was described the ultrastructure of the 
so-called “third sense organ”, probably dedicated to 
the hydrostatic pressure detection (Reverberi, 1975, 
1979). This organ is formed by a few cells bearing 
bulbous projections projected inside the cavity of the 

sensory vesicle, it was observed in many species 
and its function was related to the different ability of 
the larvae to move vertically along the water 
column. This topic was also innovative at that time: 
in fact the third organ was recently studied in 
several labs, and other hypotheses were developed 
for its function (e.g., neurosecreting cells or 
secondary sensorial neurons, Imai and 
Mainhertzhagen, 2007), but no hypotheses were 
considered more convincing than the hypothesis 
originally proposed by Reverberi. 
 
Causal analysis of embryonic development 

 
In a paper of 1939, published in Commentationes 

Pontificiae Academiae Scientiarum, with a latin 
abstract, Reverberi resumed the experiments of 
fertilization of egg fragments obtained by 
centrifugation of the egg. The centrifuged eggs were 
divided in two parts, one completely hyaline and the 
other full of granules. Only the latter, after 
fertilization, can develop even into larval stage, but 
the hyaline fragment cannot start any cleavage. 
From these observation, Reverberi inferred that the 
construction of an organism starting from the zygote 
is the result of an ordered series of biochemical 
events. During the development of the ascidian egg 
the different constituent of the egg become more 
strictly segregated (plasm segregation) (Reverberi 
and Pitotti, 1939). The further development of these 
researches, carried out with collaborators, led to the 
cytochemical study of the segregation of RNA and 
DNA. In a review of 1960, published in Advances in 
Morphogenesis, Reverberi states to trust the 
evidence that differentiating tissues have a higher 
concentration of RNA (e.g., neural tissue at neurula 
stage), but he is sceptical about a different 
concentration of DNA. In fact, at that time, the 
dispute about the constancy of the DNA content 
was still going on. Reverberi suggested that “the 
strong coloration of the nuclei of the nervous cells is 
not necessarily due to a higher content of DNA, but, 
more likely, to the fact that the nuclei are more 
condensed”. 

Interest was also shown in the mitochondrial 
respiratory enzymes. Through a very accurate Nadi-
reaction and through various cytochemical 
reactions, it was observed that many enzymes 
accumulate following mitochondrial segregation in 
the yellow crescent, in vegetal posterior 
blastomeres, and in the musculature of the larva 
(Reverberi, 1957a). The role of the enzymes in 
ascidian morphogenesis was established by 
blocking their activity with specific inhibitor. The 
main results were to ascertain a causal relation 
between the enzymatic activity and the 
differentiation of the muscular system, rich in 
mitochondrial enzymes. In fact the larvae obtained 
from the treatment with inhibitors showed a normal 
trunk, and a tail with various anomalies, all referred 
to a defective differentiation of the muscular fibers 
(Reverberi, 1957b). 

Also related to the previous ones, were the 
results of the cytochemical reaction for 
cholinesterase which can be noticed at neurulation 
not in the neural plate, as previously reported by 
other researchers, but in the muscular territories. 

 
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After the publication of these pioneer results 
(Durante, 1956), the acetylcholinesterase as a 
marker of muscular differentiation was used by 
many authors in many labs (e.g., in USA by R 
Whittaker, who visited several times the Zoological 
Institute in Palermo, and in Japan by N Satoh). 

 
Heterospecific hybridizations 

 
A lot of work was dedicated by Reverberi to the 

heterospecific hybridizations. The results highlighted 
that, in order to obtain heterospecific fertilization, the 
eggs have to be naked, without chorion and 
follicular cells. The latter not only favour the floating 
of the eggs, but have also a function in species-
specific recognizing.. 

The viable hybrid andromerogons (an 
enucleated egg of Ascidia malaca fertilized with a 
sperm of Phallusia mammillata) have only one set of 
paternal chromosomes. The morphological 
characters of the larva are, however, matroclinous, 
as the cytoplasm was “conditioned” by its nucleus 
much earlier, perhaps in the ovary. It must be noted 
that similar results have been observed in other labs 
on Echinoderms. 

Some studies carried out from 1955 to 1960 
tried to explain this phenomenon by developing the 
embryos in sea water additioned with thymidin, 
adenine etc, in order to identify possible errors in 
the syntesis of DNA and RNA. But these 
experiments were too advanced at that time and the 
transcriptomic and proteomic were still far. 

Very advanced were also the experiments on 
the fusion of the eggs of the same species or of two 
different species and subsequent fertilization with an 
heterospecific spermatozoon: giant triploid larvae 
were obtained and some time these larvae 
metamorphosed in juveniles (Farinella et al., 1969). 

In order to better understand the great interest 
of Reverberi for these studies it is important to 
remember that three chapters of his textbook 
“Introduzione all’embriologia sperimentale” (1967), 
are dedicated to the heterospecific hybridizations. 
All the problems connected with the suppression of 
one of the two sets of chromosomes or their 
maintenance and integration, the “conditioning” of 
the diploid nuclei from differentiated cells and 
transplanted in the eggs, were debated in the sixties 
and had an intellectual appeal that can be grasped 
in the textbook. It is clearly resumed in the definition 
“the egg is an equipotential armonic system”. 

In the first chapter of the above mentioned 
book, entitled “Birth and development of the 
embryology” a complex and fascinating historical 
account is outlined with clarity of style and the 
numerous Latin quotations demonstrate that 
Reverberi was a very cultured and intellectual 
person.  
 
Effects of extraneous substances 

 
Through a fusion of the two main research 

fields, the classical experimental biology and the 
chemical embryology, Reverberi also tried a new 
way of manipulating the embryos: instead of using 
the glass needles, he used some chemical 
substances. The first of these new research lines on 

ascidian embryos was carried out with a classical, 
historical substance: lithium chloride (Farinella 
Ferruzza, 1955). Treatment of unfertilized eggs 
produced normal larvae, but a treatment at stage 2 
blastomeres gave rise to larvae lacking the trunk 
and all ectodermal derivatives, like nervous system 
and palps. The treatment at stage 64 gave 
apparently normal larvae, but deprived of nervous 
system and palps. The well known “vegetalizing” 
action of lithium chloride produced the absence of 
the neural induction (Reverberi and Farinella 
Ferruzza, 1961). This research line was further 
developed and extended by some collaborators who 
also studied the effects of the environmental 
pollutants. 

Another research line was the treatment of the 
embryos with chromomycin, actinomycin D or with 
aminoacids and their analogs, in order to modify the 
quality of the aminoacid pool leading the embryos to 
produce abnormal proteins. In all these cases a 
normal development was obtained when the 
treatment was carried out before the first cleavage. 
Treatments in further stages until gastrula produced 
larvae with various degree of abnormalities 
(Bramachary and Reverberi, 1964). The results 
obtained by Reverberi, together with the other 
results obtained in those years on amphibians, sea 
urchins and chickens were fundamental to establish 
that the transcription of embryonic RNA starts at the 
blastula-gastrula stage and that the ascidians, even 
if traditionally considered examples of the mosaic 
development, “have many regulative aspects” as 
Reverberi already wrote in 1932.  

 
The ascidian embryo ultrastructure 

 
In the fifties, electron microscopy was still in a 

pioneer phase when the first papers on the 
ultrastructure of the oocytes, of the unfertilized egg 
and of follicular and test cells were published. 
Vincenzo Mancuso and his collaborators worked 
actively in this research line.  

Bearing in mind the lines of the previous 
researches, we shouldn’t be surprised that the 
electron microscopy was utilised to study the fine 
structure of the egg and of its constituents 
separated by centrifugation, in order to study 
directly what was inferred by cytological and 
cytochemical methods (Reverberi and Mancuso, 
1960; Mancuso, 1963). Once established the 
unequal distribution of principal constituents of the 
cytoplasm, their segregation was observed during 
the cleavage in lineage of blastomeres defined by 
their morphogenetic commitment. In particular, the 
cell-lineage of the muscular cells, already outlined in 
the experiments of Ortolani, was confirmed by the 
electron microscopy, from the richness in 
mitochondria of the committed blastomeres . 

I would like to mention a series papers on some 
“peroxidase cells”, so identified by Ries through 
cytochemical reactions. These cells are present in 
two rows, between the ventral surface of the 
pharynx and the epidermis, in the mature larvae 
only in the species carrying a heavy tunic, such as 
A. malaca, P. mammillata, Ascidiella aspersa. They 
have been considered of mesodermal origin, but 
Materazzi and Ortolani (1969) demonstrated that 

 
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they develop from the anterior vegetal blastomeres, 
an endodermal territory. These cells cross the 
ectoderm and join the tunic, where are probably 
active in the synthesis of mucopolissaccharids of 
the tunic. Reverberi reported the electron 
microscopy observation of these cells, just sorted 
from the endoderm and rich in Golgi apparatus and 
vesicles (Reverberi, 1971). One of my first papers 
on the ascidians, carried out with the enthusiastic 
advice of Ortolani, was about the cytoskeletal 
modifications of these “button cells” studied by 
immunofluorescence and confocal microscope while 
they penetrate the ectoderm (Sotgia et al., 1993). 
 
Immunobiology 

 
Ascidian immunobiology has recently become 

very important in the Department of Animal Biology 
in Palermo but, surprisingly there are no studies on 
this matter in the papers of Reverberi. Precisely, this 
research line began with an idea of Nicolò Parrinello 
who decided to carry out the study on serum 
proteins through immunological techniques in order 
to solve some taxonomy problems. Professor 
Reverberi understood immediately the potentiality of 
this line and encouraged him to continue. In fact, 
one of the duties of a real Master is also to support 
self-esteem and to encourage autonomy in young 
researchers! 

Naturally, speaking of Reverberi involves 
mentioning his collaborators and his School as well. 
In fact, all his students soundly developed their 
analytical skills thanks to their Master, following and 
sometimes being ahead of the new research 
orientations suggested by the technical progress in 
biological research. 

In 2003, during the first International 
Urochordate Meeting, Nori Satoh, in the opening 
lecture “Let’s move on ascidian biology with new 
ideas”, made an historical review on the ascidian 
researches and recalled the major scientists: 
Chabry (1887), Conklin (1905), Reverberi (1931) 
and his collaborators Ortolani and Minganti. 

The meaning of this historical parade was 
clearly explained during the lecture: the School of 
Palermo was leader in the experimental embryology 
for more than 50 years, mainly studying the ascidian 
development: its heraldic animal. 
 
References 
Brahmachary RL., Reverberi G. On the action of 

Chromomycin on the eggs and embryos of 
Ciona intestinalis. Experientia 20: 621-
623,1964. 

Conklin EG. Mosaic development of ascidian eggs. 
J. Exper. Zool. 2: 146-223, 1905 

Durante M. Cholinesterase in development of Ciona 
intestinalis, Experientia 12: 307-310, 1956 

Farinella Ferruzza N. Lo sviluppo embrionale delle 
ascidie dopo trattamento con LiCl Pubbl. Staz. 
Zool. Napoli 26: 42-54, 1955 

Farinella Ferruzza N, Reverberi G, Single giant 
larvae of Ascidia malaca double eggs. 
Experientia 25: 651-652, 1969. 

Imai JH, Meinertzhagen IA. Neurons of the ascidian 
larval nervous system in Ciona intestinalis: I. 

Central nervous system. J Comp Neurol 501: 
335-352, 2007 

Mancuso V. Distribution of the components of 
normal unfertilized eggs of Ciona intestinalis 
examined at the electron microscope . Acta 
Embryol. Morphol. Exper. 6: 260-274, 1963. 

Mancuso V. An electron microscopy study of the 
test cells and follicle cells of Ciona intestinalis 
during oogenesis. Acta Embryol. Morphol. 
Exper. 8: 239-251, 1965. 

Materazzi G, Ortolani G. A study of the origin of the 
cells containing sulphated acid 
mucopolysaccharides in the cephalic portion of 
the larvae of Phallusia mammillata and Ascidia 
malaca. Dev. Biol. 20: 378-385, 1969. 

Reverberi G. Studi sperimentali sull’uovo di ascidia.I 
Il comportamento e lo svilppo dei frammenti 
d’uovo di Ciona nei diversi momenti compresi 
tra la deposizione e la segmentazione. Pubbl. 
Staz. Zool. Napoli 11: 170-193, 1931. 

Reverberi G. Studi sperimentali sull’uovo di ascidia. 
II la segmentazione dei blastomeri isolate 
dell’uovo di Ciona e di Phallusia. Pubbl. Staz. 
Zool. Napoli 12: 385-406, 1933. 

Reverberi G. La segmentazione dei frammenti 
dell’uovo non fecondato di ascidia. Pubbl. Staz. 
Zool. Napoli 15: 198-216, 1936. 

Reverberi G. The embryology of ascidians. In Adv. 
Morphogen. 1: 55-101, 1960. 

Reverberi G. Introduzione all’embriologia 
sperimentale Feltrinelli, Milano, 1967. 

Reverberi G. La citocromo-ossidasi lungo lo 
sviluppo delle ascidie.Risultati che conseguono 
alla sua inibizione con azide sodico. Pubbl. 
Staz. Zool. Napoli 29:187-212, 1957a. 

Reverberi G. Some effects of enzymes inhibitors on 
the ascidian development . Acta Embryol. 
Morphol. Exper. 1: 12, 1957b. 

Reverberi G. Experimental embryology of marine 
and fresh-water invertebrates, North Holland 
Publ.Co., 1971. 

Reverberi G. Osservazioni sulle cellule “a 
perossidasi” di alcune larve di ascidia col 
microscopio elettronico Rend. Acc. Naz. Lincei 
50:795-798, 1971. 

Reverberi G. On the third sensory receptor of 
ascidian tadpole. Rend. Acc. Naz. Lincei 58: 
948-954, 1975. 

Reverberi G. On the third sensorial organ of 
ascidian tadpoles., Acta Embryol. Morphol. 
Exper. 91-99, 1979. 

Reverberi G, Farinella Ferruzza N. Lithium ions and 
brain formation in the ascidian larvae. Acta 
Embryol. Morphol. Exper. 4: 239-249, 1961. 

Reverberi G, Mancuso V. The constituents of the 
egg of Ciona intestinalis as seen at the electron 
microscope. Acta Embryol. Morphol. Exper. 3: 
221-230, 1960. 

Reverberi G, Minganti A. Fenomeni di evocazione 
nello sviluppo dell’uovo di ascidie. Pubbl. Staz. 
Zool. Napoli 20: 201-252, 1946. 

Reverberi G, Minganti A. La distribuzione delle 
potenze nel germe di ascidie allo stadio di otto 
blastomeri, analizzata mediante la 
combinazioni e i trapianti di blastomeri. Pubbl. 
Staz. Zool. Napoli 21:1-35, 1947. 

 
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Reverberi G, Ortolani G, Farinella Ferruzza N. The 
causal formation of the brain in the ascidian 
larva. Acta Embryol. Morphol. Exper. 3:296-
336, 1960. 

Satoh N. Developmental biology of ascidians. 
Cambridge University Press, Cambridge, UK, 
1994. 

Sotgia C, Fascio U, Ortolani G, De Bernardi F. 
Behavior of endodermal “button cells” during 
metamorphosis of ascidian larvae. Int. J. Dev. 
Biol. 37: 547-553, 1993. 

Reverberi G, Pitotti M. Differenziazioni fisiologiche 
nell’uovo delle ascidie Commentationes Pont. 
Acad. Scientiarum 3: 471-488, 1939. 

 

 
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