DR. MARTIN BARRY’S RESEARCHES IN EMBRYOLOGY. 
543 
pearance, also, as that preceding- the formation of discs or incipient cells in a nucleus, 
is met with, under the same circumstances, in the nucleus which gives origin to the 
embryo -f-. 
361. In the ovum Plate XXVII. fig. 232. the germ ( bs ) was in a state assisting to 
describe the mode in which the membrane f, in some instances, becomes lined with 
cells. The group (bs) seemed to consist of two portions, an inner and an outer. The 
outer portion appeared to be expanding from the inner; that is, it was apparently on 
its way to the membrane f\. 
362. Another mode in which the cells of the mulberry-like group (bs) undergo the 
local change just referred to, is seen in Plate XXVII. fig. 233. Here a process was in 
operation, destined to bring most of them into contact with the membrane f, and at 
the same time to convey the elliptic cell into a like situation. This process consisted 
in the gradual formation of a cavity at a certain part of the interior (see the figure). 
Usually, however, I have seen the changes in question to take place in the manner 
represented in my last memoir 
363. During the changes referred to in the two preceding paragraphs, the cells no 
doubt multiply by the origin of new ones in their interior |j, and in proportion to the 
extent of surface (f) which they are required to line. There is every reason for sup- 
posing that subsequently also, after reaching this situation, they increase in number 
by the same means. 
364. The facts above recorded will show that I am not enabled to confirm Bi- 
schoff’s conjecture, referred to in my last memoir: “that in the first place all the 
yelk -granules are inclosed in two, then in four, then in eight, &c. cells But these 
facts strengthen the analogy pointed out in that memoir, between the early changes 
in the ovum of the Mammifera and the divisions previously known to occur in the 
ovum of Batrachian Reptiles, and some other animals ; and it is almost superfluous 
to add, that I suppose the process in all to be essentially the same'f-f', and that it is in 
operation in the ova of other animals^. I believe it has hitherto been usual to re- 
f “Second Series,” par. 197. (Plate VI. figs. 113 to 116.56. Plate VII. fig. 121 C.). 
X Compare in “ Second Series,” Plate VI. fig. 110. with fig. 111. ; and see in that memoir remarks on the 
probable mode of origin of the cells lining the membrane f, par. 318. Note. 
§ L. c., Plate VI. figs. 111. 112. 113. 
II It will he recollected that in such a stage two nuclei were on one occasion seen in the same cell (“ Second 
Series,” l. c., par. 180. Note, par. 318. Note). 
R. Wagner’s Lehrbuch, &c., p. 101. 
tf We can now understand the very large size of the germinal vesicle as observed by R. Wagner in the 
mature ovarian ovum of the Frog (Beitriige, &c., tab. ii. fig. 6. d.). 
Professor Rathkf, says, “ The yelk of the Crustacea — and also the yelk of other animals — presents appear- 
ances, which warrant us in concluding, that at the time when the embryo forms and becomes developed, it 
[the yelk] is not merely a magazine of inert nutrient material, but rather leads a very powerful life, so that — 
at all events when the germ first arises — we might compare it to a particular organism, and subsequently to 
one of the organs of an animal being. For, in the first place, in the ova of Palcemon and Crangon, before a trace 
of the embryo is visible, the single grains, of which the yelk consists, are seen so to group themselves that they 
