534 
DR. MARTIN BARRY’S RESEARCHES IN EMBRYOLOGY. 
tainecl, are the foundations of cells ; and it is important to observe, that all the cells 
met with in the ovum in this “Third Series” of Researches, have at first the same 
remarkable form, and seem to pass through a state essentially the same as that now 
described, and which is represented in outline on a larger scale in Plate XXIII. 
fig. 177- In the ovum Plate XXII. fig. 157- the objects on the inner surface of the 
membrane f appeared to have undergone partial liquefaction. Sometimes these 
discoid objects constitute a layer of considerable thickness (figs. 160. 167.) ; at others, 
the outer discs — or cells into which the discs have passed — seem more or less broken 
down, and a globular mass of smaller discs has come into view in the interior (fig. 
162. 165.) ; and these smaller discs, in their turn, become pushed out by a fresh set 
into the external situation previously occupied by others, which have disappeared 
by liquefaction. In all the ova just referred to, there appeared to exist a central 
cavity filled with fluid. In the ovum fig. 160, a few pale globules were observed in 
this fluid. 
338. Layers of the discs or cells in question are frequently seen to have become 
circumscribed by a proper membrane — the membrane e of my “First” and “ Second 
Series.” Such was the case with the layer lying under the membrane yin the ova 
figs. 162. 164. 165. 167- In other states of the ovum no such membrane is present. 
339. It appears that one of these membranes having formed around the discs or 
cells under the membrane f, it subsequently disappears on the liquefaction of the 
objects it surrounds ; when a new set of discs or cells, taking their place, becomes in 
like manner circumscribed by a proper membrane, destined in its turn to disappear. 
In like manner several membranes (e) successively arise and disappear in a single 
ovum, as layers of discs or cells become pushed out and take the place of previous 
layers. This will, perhaps, serve to explain why some observers have never seen a 
membrane under the thick transparent membrane f ; for, as several of the figures in 
Plate XXII. serve to show, there are periods when no such membrane is present. 
CHANGES IN THE OVUM IMMEDIATELY AFTER FECUNDATION, AND BEFORE THE 
OVUM LEAVES THE OVARY. 
(These are represented in Plate XXIII. The ova there seen were of periods varying 
from 5 1 to 10 hours, and they measured in diameter from jV" to about -) 
Changes in the Position, Form, and Internal State, of the Germinal V esicle immedi- 
ately after Fecundation. 
340. It will presently be obvious that, without a knowledge of the fact that the 
germinal vesicle returns to the centre of the ovumf, it is not possible to learn the 
t This remarkable alteration — occurring while the ovum is still within the ovary — was mentioned in my 
“ Second Series,” among the facts rendering it probable that the ovary is the seat of impregnation. 
