206 DR. JAMES FOULIS. 



clusters become formed immediately below the germ epi- 

 thelium at the bottom of the sulci. A vertical section passing 

 down through such a sulcus and the group or corpuscles im- 

 mediately below it, produces the appearance as if a tubular 

 prolongation of germ epithelium was dilated at its lower part 

 into a large sac, full of developing corpuscles of the germ 

 epithelium. 



During my investigations on the structure of the ovary 

 and development of the ova, I have never found any real 

 tubular structures, neither in the human ovary, nor in any 

 other mammal that I have examined, such as the cat, dog, 

 calf, sheep, guinea-pig, rabbit, and in no instance have I 

 found Graafian follicles formed out of such structures in the 

 manner described by Pfliiger, Valentin, Spiegelberg, Wal- 

 deyer, and others. 



(d.) Develop?ne7it of the Egg Clusters. — Each egg cluster 

 is a group or collection of germ epithelial corpuscles enclosed 

 in a mesh or capsule of the ovarian stroma. 



The germ epithelial corpuscles on the surface of the ovary 

 constantly produce new elements by the process of fission, 

 and when included in a vascular mesh of stroma the cor- 

 puscles increase greatly in number by division, and from a 

 few imbedded corpuscles a large group or cluster may be 

 derived. It appears to me a most interesting and remarkable 

 observation that these corpuscles, after a certain increase in 

 number, expand or swell out into spherical bodies, an«l a 

 careful examination of the eg^g clusters has convinced me 

 that this change is brought about by the nucleus in each 

 corpuscle swelling out into a spherical vesicular body, which 

 afterwards becomes the germinal vesicle of the primordial 

 ovum, and in close contact with the wall of the nucleus is 

 gradully produced that protoplasm which afterwards forms 

 the yelk of the ovum. 



In each egg cluster we find certain individuals much 

 farther advanced in development than the rest, and these 

 appear exactly like the large primordial ova- which we 

 described as found among the corpuscles of the germ epi- 

 thelium on the surface of the ovary. Each corpuscle in the 

 cluster is potentially a primordial ovum. At the first there 

 is but a small quantity of protoplasm round the nuclei of the 

 corpuscles in each e^g cluster, but as the nuclei enlarge and 

 expand, the protoplasm round them is gradually produced in 

 considerable quantity. 



This development of the germ epithelial corpuscles into 

 primordial ova takes place in the e^^ clusters in all parts of 

 the ovary. All the imbedded germ epithelial corpuscles do 



