376 DR FOULIS ON THE DEVELOPMENT OF THE OVA, ETC. 
surrounds them. It is not uncommon to find two primordial ova in a single 
Graafian follicle, and as these eggs develope and lie in close contact with each 
other they are flattened one against the other, and a distinct zona pellucida 
may be seen round the yelk of each, although no follicular epithelial cells 
intervene between the eggs. Follicular epithelial cells, however, line the follicle 
in which these eggs are contained. 
I have failed to detect any membrane between the yelk and the zona 
pellucida. In the mature eggs, as well asin the primordial ova, large vacuoles 
are occasionally found. 
The germinal vesicle appears as a sharply defined globular body placed some- 
what excentrically in the interior of the yelk, and is about a fifth to a sixth of 
the whole egg in diameter. It possesses a delicate membranous wall clearly 
defined under high powers of the microscope. The germinal vesicle is a highly 
refractile body, and is at once conspicuous within the ovum. Within it a few 
granules and one or two distinct nucleoli are found. Ina human ovary at birth, 
very frequently primordial ova with two germinal vesicles are detected, and I 
have one specimen of the ovary of a child of two years in which a large single 
ovum contains four well-formed distinct germinal vesicles. In this case the 
yelk substance is very extensive, and completely surrounds the four vesicles. 
The wall of the Graafian follicle is in close contact with the yelk, and small 
fusiform corpuscles around this substance may be traced developing into the 
corpuscles of the membrana granulosa, but no zona pellucida is to be seen. In 
the ovary of an adult woman I have also seen a single ovum with two germinal 
vesicles, but the egg was comparatively young and no zona pellucida or complete 
epithelial investment was around it. 
The nucleolus or macula germinativa is said to be always present in the 
primordial egg. The presence of two or three germinal spots in a single germinal 
vesicle has often been noted. Besides the germinal spot a few minute corpuscles 
are occasionally seen in the germinal vesicle. By some the germinal spot is 
thought to be a solid body, and by others it is considered to be of the nature of a 
vesicle, and I have seen round it an extremely fine linear investment. In the 
cat’s ovum very frequently a minute bright spot or vacuole is noticed in the 
germinal spot. Scuron described this as a solid body, and termed it the 
“oranule.” (KORN). 
GENERAL CONCLUSIONS. 
- The following general conclusions have been arrived at in the course of my 
investigations :— 
The corpuscles of the germ epithelium are derived by direct proliferation 
from those columnar corpuscles which invest the median side or surface of the 
Wolffian body, and which are continuous with the layer of columnar corpuscles 


