356 DR FOULIS ON THE DEVELOPMENT OF THE OVA, ETC. 
the stroma appears as large as a florin or a half-crown piece, and the nucleus or 
germinal vesicle as large as a threepenny or fourpenny piece. Between these 
two extremes young ova in all stages of development may be seen in the stroma 
of such a young ovary. The change which the germ epithelial corpuscle under- 
goes during its development is the following :— 
As soon as the corpuscle is imbedded in the stroma, its nucleus swells up 
into a round or spherical body, within which generally appears a spot or 
nucleolus. The nucleus presents a sharply defined limiting membranous wall, 
and becomes the germinal vesicle of the future ovum. Immediately around 
the nucleus is gradually produced that protoplasm which afterwards constitutes 
the yelk of the mature egg. Jn all paris of the ovary, wherever we examine such 
young developing ova, we find fusiform corpuscles, like the fusiform corpuscles of 
which. the stroma is composed, lying in contact with the protoplasm which 
surrounds the nucleus or germinal vesicle. 
The youngest egg clusters are immediately below the germ epithelium, and 
many of them are in connection with it. These latter have not, as yet, been 
completely closed in and separated from the germ epithelial layer by the 
connective tissue bundles of the stroma. 
The clusters of corpuscles in connection at their upper parts with the germ 
epithelium differ considerably from each other, both in size and form. Some 
are oval and elongated, others are spherical. Many of them are larger at their 
lower and middle parts than at the part in connection with the germ epithelial 
corpuscles. If a vertical section passes down through such clusters as these, 
such as are swollen out at their lower and middle parts but narrow at their 
upper parts, we have presented under the microscope the appearance as if 
bottle-shaped tubes full of round corpuscles extended from the germ epithelium 
downwards into the stroma of the ovary. These appearances are often seen, 
and it is important to study them well. It will be remembered that PrLtcEr* 
described in the young kitten’s ovary numerous tubular processes passing down- 
wards from the surface of the ovary into the stroma, in which the germinal 
vesicles originated, and by the successive divisions of which Graafian follicles 
containing eggs were formed. I have very carefully examined the ovaries of 
kittens and puppies, but have failed to find any tubular processes of epithelium 
passing into the stroma from which Graafian follicles are formed, and it appears 
to me that PFLUGER is incorrect in stating that such exist in the ovary of the 
kitten. 
In section, the ovary of a kitten at birth presents a structure very similar to 
that of the ovary of the two to three weeks’ old kitten, but we find in the germ epi- 
thelium layer very few primordial ova. Many large spherical nuclei, with a thin 
film of protoplasm round them, are seen among the germ epithelial corpuscles, and 
* Pricer, “Die Eierstécke der Saiigethiere und des Menschen,” Liepzig, 1863, p. 4. 


