546 
DR. MARTIN BARRY’S RESEARCHES IN EMBRYOLOGY. 
a very different interior and form. Some of these cells are shown more highly mag- 
nified in Plate XXVIII. fig. 253. a . ; which presents also a portion of the membrane f. 
Some of the same cells (fig. 253. 8.) were observed lying near the ovum. These cells 
had sent out processes, which at « were seen to have become interlaced, and in 
part to have coalesced. A central pellucid space, present in each of these cells, and 
originally round ((3), had changed its form in many of the cells «, and seemed to be 
following the direction of the interlacing processes. These cells having gradually 
collected around the thick transparent membrane (f), and interlaced, by coalescing 
form the incipient chorion. 
373. In fig. 252. is seen a state rather earlier than that in fig. 253 f. Here (a) the 
pellucid centres were still round, and the interlacing arms or processes of the cells 
had scarcely begun to coalesce. At (3 in this figure are some of these cells which had 
a more superficial situation on the same ovum. They were not so close together as 
the preceding (a), to which they had probably been added. It appears indeed to be 
by additions of cells, thus made externally, that the chorion thickens (see Plate XXVI. 
figs. 211. 212, Plate XXVII. figs. 229 to 234. cho.), and it would not be easy to de- 
termine when these additions cease, or indeed whether they cease at all before the 
addition of villous tufts, which I am very much disposed to think are formed by the 
same kind of cells. These cells will be particularly referred to in a future paper;};. 
374. In Plate XXIV. figs. 186. 187 and 189. the incipient chorion is seen to have 
been just beginning to imbibe transparent fluid, and to rise from the membrane f. 
Whether the so-called “disc” brought, with the ovum from the ovary contributes to 
supply this fluid, I do not know ; but when the chorion is in an incipient state, many 
of the cells of the “ disc” are sometimes found lying around it ; and in other instances 
there is in the same situation, a transparent fluid, which may possibly have arisen 
from the liquefaction of those ovarian cells. 
Application of some of the foregoing Facts to the Physiology of Cells. 
375. Existing views regarding “cells” have been already briefly stated (par. 324). 
The Appendix contains them more in detail. 
376. Presuming that what is known regarding cells warrants the conclusion that 
they have essentially the same structure in animals and plants, I offer the following 
remarks as applicable equally to the animal and vegetable cell§. And as researches 
have hitherto related chiefly to the cells of plants, I shall refer for the most part to 
what has been published respecting these. 
3 77- That I have found the nucleus at the surface of its cell, is shown by figures 
in the present and in the two preceding memoirs. As this, however, rarely continues 
to be its situation at the period I have investigated, it may be proper to compare my 
t Fig. 252. was taken from an ovum of 11 hours; fig. 253. from an ovum of 14 hours. 
\ I think it very probable however that there is an origin of new cells within those already coalescing. 
§ Except in those instances where reference is made to structures belonging exclusively to plants. 
