The Transition of Peritoneal Epithelial Cells
into Germ-Cells in Gallus Bankiva.
By
J. Bronte Gatenby, M.A. (Dubl.), D.Phil. (Oxon.),
D.Sc. (Lond.),
Professor of Zoolog}7 and Comparative Anatomy, Dublin University.
With Plate 1 and 1 Text-figure.
INTRODUCTORY.
THE question of the origin of the germ-cells in the Vertebrata is still one of the most hotly contested problems in
Embryology. It is hardly necessary for me to comment on
the two main views. Shortly stated, one group of observers
(Nussbaum, Hoffman, Eigenmann, Woods, Allen, Beard, King,
Swift, Jordan, and others) considers that the germ-cells arise
early in embryo-formation, take no part in the histogenesis,
are carefully set aside and eventually give rise to the gonads
of the individual; this group of observers claims to have
traced the germ-track from very early stages onwards, and
denies that peritoneal (coelomic) epithelial cells could metamorphose into cells which ultimately give rise to eggs and
spermatozoa. The modern adherents of the other group
(Waldeyer, Balfour, Semon, D'Hollander, Felix, Dustin, Firket,
Gatenby, and others) either deny that an early segregation
and subsequent migration of germ-cells takes place, and
consider that germ-cells are formed at the expense solely of the
germinal (coelomic) epithelium, or admit partially or wholly
the migration point of view, but insist that secondary sets of
germ-cells are formed later by metamorphosis of peritoneal
epithelial cells.
NO. 209
B
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J. BRONTE GATENBY
He would be either obstinately shutting his eyes to a truth,
or would be ignorant of the literature, who would nowadays
attempt to deny that the early segregation of some germ-cells
in the yolk-sac wall and their subsequent migration to the
' genital ridges ' is not a proven fact. With Felix, Dustin,
Firket, Berenberg-Gossler and I are prepared to admit that
some germ-cells have an endodermal origin, or at least an
origin antedating that of the germinal epithelium; but the view
more preferable to us is that such migration is a minor phenomenon in the total history of the gamete formation of the
organism. Felix, Dustin, Firket, and Berenberg-Gossler consider that the occurrence of primordial germ-cells in the yolksac endoderm and their movement to the mesoderm is a fact,
but a fact of only phylogenetic importance.
I have never in any of my published papers attacked the
problem in a partisan manner ; by examination of the peritoneal epithelium I showed that in Amphibia new eggs are
formed during adult life, and I claimed that these eggs had
arisen by metamorphosis from germs derived from peritoneal
epithelial cells. I have never stated that the migratory
behaviour of yolk-sac cells has not been correctly described by
certain authors. I have not myself worked especially at the
germ-cells in embryonic cells, though I possess and have
carefully examined sections of selachians, frogs, and birds at
these early periods, and consider that what Woods, Allen,
Swift, and Jordan describe is probably true. But the origin
and nature of the pockets of cells already described by me (7)
in the germinal epithelium of a female frog during the early
summer months remains to be explained on their view.
In a recent paper (15) Jordan describes the embryonic
history of the germ-cells of C a r e t t a c a r e t t a , the loggerhead turtle. Jordan, in agreement with his predecessors
who have lately examined embryonic stages in the chick,
turtle, selachian, and frog, finds certain evidence of migration
of early germ-cells of the yolk-sac into the region of the future
gonad. Jordan declares bluntly that he considers that my
figures give no adequate support of my claim that mesoderm-
GERM-CELLS IN GALLUS
d
cells transform into germ-cells, b u t d o e s n o t s a y w h a t
f o r c e s h i m t o t h i s c r i t i c i s m . In his last paragraph
(p. 339) Jordan says : ' But many more researches covering
the later periods of the history of the ovary with special
reference to the so-called " germinal epithelium ", such as
those of Swift on the chick and of Gatenby on the frog, are
needed before the hypothesis of a germinal path for vertebrates
can be said to be completely established. In view of the
conditions in the gonads of certain annelids, molluscs, and
echinoderms, where enormous numbers of germ-cells are
formed during successive years, and the disagreements which
still exist with respect to such relatively simple forms as frog
(Allen and King v. Dustin and Gatenby), chick (Swift v. Firket),
and the turtle, C h r y s e m y s (Allen v. Dustin), the claims that
two series of genital cells occur—a primordial and a secondary
or definitive . . . cannot perhaps be said to have been definitely
disposed of.'
It would almost seem as if most of those observers who have
supported the ' germ-path ' hypothesis had done so because
they began their work convinced of the truth of the theory of
the continuity of the germ-cells and of the germ-plasm. Their
minds are already made up ; unfortunately, therefore, they
are a little prone to deny without a fair hearing any evidence
produced by the opposing side.
To their minds the organism is like a military machine. The
germ-cells are peripatetic and march up the mesentery in
strings and platoons ; nothing else in the organism but these
peripatetic cells can become gametes—no indifferent mesenchyme or coelomic epithelial cell can transform into a germcell. The fact that these cells have taken a small part in the
formation of any region of the soma (such as the coelomic
epithelium) at once puts them out of the pale or charmed
circle of those cells which can become germ-eells.
Lately a fowl has come into my possession, which on examination proved to be changing in sex. A new testis was in process
of formation within and in front of the old ovary ; the latter
contained haemorrhagic areas. The case I have to describe is
B2
4
J . BRONTE GATBNBY
particularly relevant, because, of all the intersexual birds
described,1 it seems to be the only one which shows such
remarkable activity outside the gonad.
PERSONAL WORK ON THE DOMESTIC FOWL.
In a previous paper 2 (Gatenby and Brambell, 10a) the
genitalia of this hen have been described. There was a diseased
atrophic ovary on the left side of the hen, and just in front of,
but outside, the old gonad, were two areas of newly-forming
testicular tissue the size of a wheat seed. In both areas the
process was so little advanced that all stages of the metamorphosis of peritoneal cells into germ-cells could easily be
found.
The peritoneal epithelium in the region of the hen's gonad
consists of several layers of squamous fibrous cells, as shown
in PI. 1, fig. 5, below the figure 1. As has been pointed out
elsewhere (10 a), the suprarenal in birds may be in close
proximity to the gonad, and may in certain cases be in cellular
continuity with the latter, and in the case described in this
paper the large flakes of thickened epithelium not only lie
inside the ovary, but pass over the suprarenal, two tubules of
which are shown in PI. 1, fig. 6, the active areas being at TA.
All the figures on PI. 1 are drawn from sections of material
fixed in formalin followed by Bouin's fluid and Mann's methyl
blue eosin, and they show the chromophility reactions of the
cells in question.
The cells of the peritoneal epithelium are almost entirely
basophil, the only question being as to the real condition of
the nucleolus : the latter in the majority of cells is basophil,
but in others is amphophil with basophil preponderance. An
obvious and well-developed plasmosome is never present in
these cells.
Underlying the upper layer of much-stretched cells of the
peritoneum are found numbers of more rounded, less fibrous
1
See Crew, ' Trans. Roy. Soc.', 1923, and Miss Fell, ' Brit. Journ. Exp.
Biol.'. 1923.
2
Shortly appearing in the ' Journal of Genetics'.
TEXT-FIG. 1.
CY
, 10 mm.
A
Text-fig. 1, a, shows the ordinary peritoneal epithelium near the
region of the newly formed testis. The cells are flattened and
there are several layers : cell walls cannot be distinguished.
Text-fig. 1, b, is from a region just near the testis, where the
peritoneum is proliferating new germ-cells : at pa are ordinary
peritoneal cells, which lower down have formed the large rounded
nuclei at the Arabic numeral 3 : such cells have a distinct cytoplasm (CY) which in older cases becomes very granular. Cells
intermediate between these new germ-cells and the peritoneal
cells are marked by the Arabic numerals 1 and 2. Fixed in
formalin and Bourn, stained in iron alum haeraatoxylin. The
arrow points to the peritoneal cavity.
6
J. BRONTE GATBNBY
elements, which have been identified as the forerunners of the
new generation of germ-cells : it should be noted, however,
that in some regions whole sections of peritoneum metamorphose into germ-cells, all layers being involved in a thorough
manner.
In Text-fig. 1 a is a typical region of the peritoneum, taken
from a spot near the newly-forming testis. The fibrous nature
of the cells is noticeable : no cell walls can be made out in
such preparations. This is the common experience of the
histologist who has examined tightly drawn-out pavement
epithelial cells : silver nitrate reduction alone would show cell
walls at this stage.
In Text-fig. 1 b is a region of the peritoneum where metamorphosis of the flattened cells is in progress : the cells marked
by the Arabic numeral 3 nearly corresponds to the cell drawn
in PI. 1, fig. 1. In Text-fig. 1 b stages leading to the formation
of gerrn-cells are marked by the Arabic numerals 1 and 2.
The new cytoplasm (CY) is now either marked by a distinctcell wall or by the possession of granules, but in such preparations the cell Avails of every cell cannot be made out.
In iron haematoxylin preparations the granulation of such
cells as that in Text-fig. 1 b, 3, increases in strength gradually
till it shows as grey or grey-black.
Discrete, strongly staining mitochondria now appear, I know
not how.
In PI. 1 the changes leading to the formation of a spermatogonium are followed out in preparations stained in Mann's
methyl blue eosin. Pig. 1 is a typical underlying peritoneal
epithelial cell: it has a definite cytoplasm and not the fibre-like
cytoplasm of most peritoneal cells. In many peritoneal
epithelial cells, even the most highly differentiated ones as of
fishes and frogs, it is always possible to find a granular cytoplasm around the nucleus, even though the rest of the cell is
a fibre of some sort. In birds, however, it is generally impossible
to find this granular part, except where the cell is not included
in a much stretched region. PI. 1, fig. 1, has a basophil cytoplasm containing many watery vacuoles.
GERM-CELLS IN GALLUS
I
In the next stage of metamorphosis the amount of granulation in the cytoplasm increases very considerably, and from
a basophility the cytoplasm and its contents gradually pass to
amphophility, as shown in PL 1, fig. 2. From amphophility
these cells pass to complete oxyphility. Masses of such cells
lying between the layers of peritoneal epithelium form most
conspicuous objects, and an example is shown in PI. 1, fig. 5,
at a low power ; there are many cells marked a, b, and c,
which are crammed with amphophil granules having oxyphil
preponderance. Such cells divide to form the spermatogonia
shown in PI. 1, fig. 4. The cytoplasmic granules gradually
become less prominent and tend to form a pale irregular
network, which finally passes imperceptibly into a form of
cytoplasm with no granules clearly perceptible.
These stages are shown in PI. 1, fig. 5, a, b, c, and d.
The behaviour of the nucleolus is interesting, for a very
clearly marked plasmosome appears soon after the peritoneal
cell has begun to metamorphose. Peritoneal cells do not possess
any well-marked nucleolus, but soon after the peritoneal cellnucleus has become spherical, a karyosome appears (PL 1,
fig. 1). As the cell metamorphoses this karyosome loses its
basophility step by step, and becomes amphophil (PL 1, fig. 2).
When the germ-cell is formed its nucleus contains a plasmosome
derived from this amphophil nucleolus, as well as a basophil
net-knot attached thereto (PL 1, fig. 3). Every sperrnatogonium has a plasmosome and one or two net-knots.
THE MITOCHONDHIAL GEANULES DURING METAMORPHOSIS
OP PERITONEAL CELLS.
In the frog the most attenuated peritoneal cell contains
a small granular cytoplasm with mitochondria and Golgi
bodies. In such cases the metamorphosing peritoneal cell
merely becomes more granular, and the mitochondria increase
in number.
So far as the bird is concerned it is very difficult to discover
any granular cytoplasm in the peritoneal cells ; the latter are
so attenuated that no microscopical examination of my present
8
J. BRONTE GATENBY
material revealed any mitochondrial constituents; yet the
newly metamorphosing cells contain mitochondria. Whether
the latter arise d e n o v o in the cytoplasm, or from the nucleus,
or whether there are mitochondrial remains left in the peritoneal cell, which regenerate the new granules, could not be
discovered.
A.
DISCUSSION.
It will be noted from the present description of the hen's
newly formed gonacl, that the prophases of the heterotypic
division do not occur till after the new avian germ-cells have
become arranged into spermatic tubules. In none of my
material are the cells sufficiently advanced to undergo the
prophases.
Miss Pell in one of her examples shows the prophases of the
heterotypic division taking place directly after the metamorphosis of the peritoneal cells (Miss Fell, PI. i, figs. 5 and 7).
In one case, however, we are dealing with genital sex-cords, in
the other with direct metamorphosis of extra-genital peritoneum
into germ-cells. Miss Fell's examples in figs. 5 and 7 resemble
the sex-cords of the young mammalian ovary, or some of the
germ-pockets already described by me in the frog (Gatenby, 7) ;
in both these cases, too, the new cells proceed to the prophases
without an intervening multiplicatory phase.
Miss Fell's fig. 5 of newly forming sex-cords suggests ovarian
tissue rather than spermatic, for surely in spermatic tissue one
always finds a multiplicatory phase during the resolution into
tubes ? Miss Fell's diplotene and pachytene stages put
beyond all doubt her claims that these ingrowths are sex-cords
and not adenomatous growths, and in the case which I have
described in the present paper no question of disease of the
special proliferating region of the peritoneum is involved.
One cannot help thinking that the sex-cords described by
Miss Fell in PI. i, fig. 5, are somewhat intermediate between
the testicular and the ovarian type. This is merely a suggestion
which may be of no value. It would also be interesting to
know the behaviour of the cytoplasmic inclusions in her cases.
GERM-CELLS IN GALLUS
9
The followers of Nussbaum have denied that any cell which
had become included in the formation of the soma could
de-differentiate and subsequently form a germ-cell. I have
shown elseAvhere, both by cytological method and by counting
the number of oocytes in the ovaries, that no frog ever possesses,
at any one time, the large number of eggs which it lays in a
lifetime.
The evidence for the fowl is also complete, for in this paper it
has been shown that the new testis which was forming both inside
and outside the old haeniorrhagic ovary was derived directly by
transition from peritoneal cells. Dr. Crew and Miss Pell in their
independent papers have come to the same conclusion, and Miss
Fell has given photographic proof in her valuable contribution.
B.
DISCUSSION.
The problem of the origin of the germ-cells in the Metazoa
is of first-rate importance; it touches very largely upon
a considerable tribe of theories, hypotheses, and half-digested
speculations, which, on a practical basis, were started by
Nussbaum and chiefly added to by Weismann.
The ' germ-track ' (Keimbahn) determinants in insects, so
ably treated by Hegner, provide a beacon around which flutter
all modern germ-path theorists.
The A r t h r o p o d a especially provide nearly every example
of ' germ-track ' determinants known. The early segregation
of the germ-cells of some insects in the posterior pole of the
egg, generally around the germ-cell determinant, is well known;
I refer to papers by Lecaillon (see 12), Hegner (13), Silvestri
(see 9), Gatenby (9), &c. Hegner has carefully collected all the
cases of reputable and fairly reputable occurrences of ' germtrack ' substances. Examination of Hegner's apparently
formidable list, however, shows that of the properly established cases eleven out of eighteen are Holornetabolous Insecta ;
this refers to pole granules in ova. Nearly all the reputable
cases of ' germ-track ' determinants in eggs are from the
A r t h r o p o d a or from the N e m a t o d a . Sagitta is a wellknown case from the C h a e t o g n a t h a . Two cases quoted by
10
J. BRONTE GATENBY
Hegner of niitochondrial ' germ-track ' determinants in the
chick and guinea-pig are unlikely, and both have since been
rejected by workers who would keenly have desired to confirm
Eubaschkin and Tschaschkin (16, 18). I refer to Swift and
Jordan (15,11?). The latter, in C a r e 11 a (a turtle), says: ' There
is no evidence in C a r e t t a of a differential mitochondrial content between the germ-cells and somatic cells, as maintained
by Tschaschkin in the case of the chick, and by Eubaschkin
in the case of certain mammalian embryos, and as denied by
Swift and von Berenberg-Gossler.' All this reinforces me in
my contention that no histological differences exist between the
early germ-cells of embryos and adults and between the
somatic cells of the gonad in vertebrates. The statement that
food-yolk constitutes any valid difference between germ-cell
and somatic cell is inadequate and only of very comparative
value in certain exceptional forms.
Even though the Insecta furnish many remarkable examples
of ' germ-track' determinants we must remember that in
not all insects are such substances found. In P h y l l o d r o m i a , a cockroach, studied carefully by Heymons,
secondary germ-cells are described as arising from the coelom
blocks, and no ' germ-track ' substance was found.
Moreover, it must be remembered that the insects are a very
special group whose developmental history is much modified.
In the holometabolous insects, say a parasitic Hymenopteron,
where the ' germ-track ' determinant is so well marked, there
is every necessity for an early preparation of the egg for
segmentation and for a previous laying down of organ-forming
areas, because the development of the Holometabola nearly
always must take place within a certain set time and season.
The egg is laid out to form the larva at the quickest rate, and
while the young larva is feeding the imaginal rudiments are
forming. Hence the provision of ' germ-track substances '.
The germ-cells in the holometabolous Insecta must be provided
with yolk or some sort of food to keep them either independent
of the already occupied somatic cells, or to enable them to
go on with their development synchronously with the somatic
GERM-CEIiLS IN GALLUS
11
cells. Hegner (12) shows that in M i a s t o r the germ-cells,
segregated early and provided copiously with germ-cell
determinant substances, except for short pauses go on dividing
and developing during the time the germ-layers and other
organs are in process of formation. Unless they were provided
with nourishment they could not do this. I am aware, however,
that in many forms with germ-cell determinants the germ-cells,
after segregation, remain quiescent till much later, but before
they have been long segregated the determinant has disappeared
as such.
I therefore conclude, with regard to the pole-cell determinants
in Arthropods, that such substances are essentially of a special
nutrient nature, and are provided in order to allow the germcells independently to rest or to develop further. The somatic
cells do not need such special foods in Insecta, because the
yolk-cells provide them : the question might then be asked,
why, if the germ-cells are to be placed in the same rank as the
somatic cells, do not the former become provided with nourishment in the same way as the latter ? The answer to this
I would consider to be : That it is necessary for the organism
to provide specially for the germ-cells in order to prevent the
latter from being caught up in the stream of differentiating
somatic cells, whose influence otherwise would cause the germcells to lose their individuality and take part in the formation
of some highly differentiated organ. If such a ' catching up '
of the germ-cells into the formation of some layer or organ
took place, the animal would automatically become sterile,
and this applies especially to insects where all the egg and larval
material is most meticulously laid out for the formation of
definite areas in the adult. In my work on the development
of T r i c h o g r a m m a e v a n e s c e n s (10) I was able to show
that at first about thirty-five cells went to form the endoderm,
just as it was found that between six and nine cells form the
future gonad (germ-) cells. It might further be assumed that
the germ-cell determinant contains some enzyme or other
substance which suppresses the germ-cells during embryo
formation, and keeps them isolated.
12
J. BRONTE GATENBY
It should, however, be noted that the position of many
of the Insecta and of the Vertebrata is quite different, and
in the following way. In Insecta development in relation to the
coelom is specially modified ; now, the coelom throughout all
the Coelomata is closely associated with the production of the
germ-cells ; in such Insecta as the parasitic H y m e n o p t e r a
and others, where the germ-cell determinant is important,
there are no proper coelom blocks formed, and the mesoderm
generally consists of scattered cells. The germ-cells are
divorced from the coelom, and since the latter can no longer
produce them later on at the correct period, there must be
another provision made for them. If it is then asked, why in
vertebrates, where the coelom is well developed, should there
be any early segregation of germ-cells possibly antedating the
coelom, the answer might be found in Berenberg-Gossler's
suggestion that such migration of early germ-cells is merely
the dilatory development of mesoderm from the endoderm (3).
It is doubtful in some animals if these primordial germ-cells
ever live to form gametes.
Child, in his extremely suggestive and interesting work on
' Senescence and Eejuvenescence ', says (p. 356) : ' There is
no proof of the " segregation of the germ-plasm " as an independent entity in embryonic development, but the germ-cells are
very evidently determined like other parts of the body by
correlative factors. Moreover, the course of development of
the gametes bears every indication of being a progressive
differentiation and senescence, not fundamentally different
from that of other organs of the body, and the fully developed
gametes are physiologically old, highly differentiated cells,
which are rapidly approaching death and in most cases actually
do die soon after maturity unless fertilization occurs.'
Hegner (12) himself, apparently an ardent believer in the
germ-plasm significance of ' Keimbahn' determinants, has
shown in his experiments with beetles' eggs that in the insect
egg ' no regeneration of the part which would have been produced by the killed region (killed by a hot needle) takes place '.
This applies apparently to a n y p a r t of the egg. If the pole
GERM-CELLS IN GALLUS
13
region, where the ' Keimbahn ' determinant lies, is killed, the
formation of an embryo without germ-cells is the result ;
this is very significant, but must however be read alongside
other statements made by Hegner, which show that if the
head end of the egg be killed no head develops. If any part of
the blastoderm be destroyed, the organ or part which would
have been produced by this is not regenerated and is absent.
In fact Hegner proves Child's statement that the ' germ-cells
are very evidently determined like any other parts of the body '.
What is the so-called germ-cell determinant in H o 1 o m e t a b o 1 a ? Is it not merely a nutrient mass ? In my paper
(9) on the segregation of the germ-cells in T r i e ho g r a m m a
e v a n e s c e n s , I took the view that the germ-cell determinant in this form, t}rpical of all parasitic H y m e n o p t e r a ,
is a yolky body, supplied to the germ-cells to keep them
nourished and quiescent, while the other cells in the body were
forming the embryo.
If certain organ-forming substances do go in the egg to form
the future gonad, this does not force us to the belief that there
is a germ-path. The organ-forming substances are laid down
in the egg by the oocyte nucleus during oogenesis. The egg
segments and special regions of it go to form, special organs,
but if one denies that in the after-life of the embryo a somatic cell
could become a germ-cell under the proper stimulus, one simply
limits the power of the cell-nucleus in an unjustified and
absurd manner.
Hegner showed that when any part of the blastoderm in
the insect egg (C a Hip h or a) was killed no regeneration of
the part took place ; if the head or anterior end of the egg was
killed the larva developed without a head ; in polyernbiyonic
species of H y m e n o p t e r a always the head end (and all the
outer layer in some cases) of the egg is deputed to form the
future embryonic membrane. The embryos do not, however,
grow up without heads ; in the non-embryonic species of
Platygasters the outer cortical layer of the egg is delaniinated
to form an embryonic membrane. In fact just the parts which
in Hegner's experiments, when killed, did not regenerate, are
14
J. BRONTE GATENBY
here normally rejected ! It is all a matter of cell potentiality
and cell differentiation which compel a given living unit to
follow a certain path for the time being.
It is therefore unnecessary to labour the matter further,
but if Ave accept the view that somatic cells do metamorphose
into germ-cells, we at the same time must entertain some
further assumptions. It is possible that a somatic cell metamorphosing into a germ-cell might ultimately produce gametes
whose physiological and genetical tendencies would be quite
different from those of the earlier normal germ-cells : in such
a way new variations might be produced.
Moreover, peritoneal cells which have been exposed to
a lifetime of stress,, disease, and poisonings of various kinds
might easily carry the effects of their treatment on to the next
generation.
SUMMARY.
1. In a fowl ( G a l l u s b a n k i v a ) which possessed some
male characters (comb, wattles, and male pugnacity) the ovary
contained an adenoma and was atrophic.
2. Within this effete ovary the peritoneal epithelium had
begun to elaborate new testicular tissue. Certain regions outside
the gonad contained metamorphosing peritoneal epithelial cells.
3. The transition of avian peritoneal cells into germ-cells
takes place in a manner similar to what has already been
described in A m p h i b i a (Gatenby).
4. The basophil peritoneal epithelial cell, at first clear,
becomes granular. Its nucleus becomes spherical and a pure
nucleolus appears : the cytoplasmic granules pass from basophility to oxyphility.
5. At this period the cells divide and the oxyphil granules
gradually dissolve into a smooth oxyphil ground cytoplasm.
The cells, after division, are found to be arranged in columnar
manner as spermatic tubules.
6. In each tubule a lumen appears at a later period.
7. Attention has been drawn to the work of Dr. Crew and
Miss Fell, who have already described the metamorphosis of
peritoneal cells into germ-cells.
GEEM-CBLLS IN GALLUS
15
DESCEIPTION OF PLATE 1.
All figures have been drawn from preparations fixed in
formalin and Bouin's fluid and stained in Mann's methyl blue
eosin, except figs. 5 and 6. They were drawn with a Koritska
1/14 oil immersion, and a Gifford orthochromat, F = 9 m / m ,
eye-piece ; fig. 5, 6 comp. eye-piece X 1/14 oil immersion ;
fig. .6, 2 Hugh, eye-piece X 1/14 oil immersion.
LETTEBING.
G, cytoplasmic granule, not mitochondria!, N, nucleolus. XP, amphophi]
nucleolus. PL, plasmosome. BV, blood-vessel, SPQ, spermatogonium.
TA, pockets of metamorphosing peritoneal cells, OT, connective-tissue cell.
SB, suprarenal.
Fig. 1.—Peritoneal cell in process of metamorphosis into a germ-cell.
A basophil granulation has begun to appear.
Fig. 2.—Next stage : granulation denser and amphophi], nucleolus
amphophi].
Fig. 3.—Next stage : granulation oxyphil, plasmosome well marked.
Fig. 4.—Spermatogonial cells after division of such a cell as shown in
PI. 1,fig.3.
Fig. 5.—Peritoneal epithelium with germ-cells forming, and underlying
spermatogonia (SPO).
Fig. 6.—Lower power drawing of peritoneum to show general appearance
of proliferating areas (TA) and spermatic tubules (SP) in an area underlying
the suprarenal.
BIBLIOGRAPHY.
References not given here may be found in the papers of Jordan, Galenby,
and Hegner.
1. Allen, B. M.—" The Origin of the Sex-cells of Chrysemys marginata ",
' Anat. Anzeiger ', Bd. 29, 1906.
2. •
" The Origin of the Sex-cells of Amia and Lepidosteus ", ' Journ.
Morph.% vol. 22, 1911.
3. Berenberg-Gossler, H.—" Ueber Herkunft und Wesen der sogenannten primaren Urgeschlechtszellen der Amnioten ", ' Anat. Anz.',
Bd. 47, 1914.
4. Dustin, A. P.—" L'origine et Involution des gonocytes chez les
Reptiles ", ' Arch, de Biol.', torn. 25, 1910.
5. Felix, W.—" Die Entwicklung der Keimdrusen und ihrer Ausfiihrungsgange ", £ Handb. d. Entwick.', von O. Hertwig.
16
J. BRONTE GATENBY
6. Firket, Jean.—" Recherches sur I'organogenese des glandes sexuelles
chez les oiseaux ", ' Arch, de Biol.', torn. 2, 1914.
7. Gatenby, J. Bronte.—" The Transition of Peritoneal Epithelial Cells
into Germ-cells in some Amphibia, Anura, especially in Rana
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Wash., 1917.
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Quart. Jouni. Micr. Set.
Vol. 68, N.S.
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PL 1.