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DR. MARTIN BARRY’S RESEARCHES IN EMBRYOLOGY. 
328. As the foundations of new cells successively make their appearance in the 
interior of the altered germinal spot, the pellucid central cavity in the latter presents 
changes in its size, and sometimes is scarcely or not at all to be discerned (compare 
in Plate XXII. figs. 161 and 166.), whence I conclude that the foundations of new 
cells in question, have their origin in the pellucid fluid of that central cavity. This 
remark applies to all the nuclei referred to in this memoir ; and I apprehend it will 
be found, in connection with what has been stated in the preceding paragraph, that 
the nature and the varying appearance of the nucleolus of Dr. Schleiden may be 
thus explained. 
329. Each of the objects in the germinal vesicle (c) which I have called cells or 
incipient cells, presents with more or less distinctness, an interior indicating the ope- 
ration there of a process essentially the same (see Plate XXIII. fig. 169.) as that which 
gives origin to the concentric layers, in one of which the object itself is contained. 
330. The germinal vesicle passes from the globular into a flattened form-f'. In the 
ovum, Plate XXII. fig 158, it resembled in its form the crystalline lens of the eye 
(fig. 159.). It also becomes very much enlarged^. 
331. The position of the germinal vesicle does not change, but it becomes more 
determinately applied to the investing membrane than in the immature ovum ; whence 
the peculiar form of this vesicle in fig. 159. The pellucid part of the altered germinal 
spot, at which the foundations of new cells arise, is directed towards the surface of the 
ovum (figs. 156 to 167-)§- More particularly, the part in question is directed 
towards an attenuated region or an orifice (figs. 165. 167-), to be presently mentioned 
as observed in the thick transparent membrane f. In one or two instances, indeed, 
this part appeared as if protruded into the orifice ; and I could not discern a conti- 
nuation over it of the membrane of the vesicle. 
Preparatory Changes in the thick transparent Membrane , or “ Zona Pellucida .” — 
The Point of Fecundation. 
332. In my “Second Series,” it was stated that I had found Spermatozoa on the 
ovary || . From the facts just mentioned, and those about to be recorded, it may, I 
think, be inferred that the fecundating element of the seminal fluid penetrates, not 
only into the ovary, and into the interior of the ovum, but into the germinal vesicle, 
pearance after maceration (“ Second Series,” l. c., Plate V. fig. 89. 5.), for each of the several layers of incipient 
cells into which a nucleus resolves itself, we shall hereafter find frequently to become circumscribed by a 
proper membrane. 
t Resembling that figured by R. Wagner in a very mature ovarian ovum of the Frog. (Beitrage zur Ge- 
schichte der Zeugung und Entwickelung, tab. ii. fig. 6. d.). 
\ See the Table of Measurements, par. 429. 
§ R. Wagner remarks, with reference to the unaltered spot, that it appeared to him to be always directed 
towards the surface of the ovum (Beitrage, &c., p. 24.). 
|| A note was added, yielding the priority of this discovery — made, however, in another Mammal, the Dog — 
to Professor Bischoff. 
