202 DR. JAMES FOULIS. 



with Remakes middle plate, it likewise has an investment of 

 similar corpuscles. The first appearance of the ovary is the 

 thickening of this columnar epithelium on the median side 

 of the Wolffian body (Waldeyer). At the commencement 

 of this thickening there is seen under it a small out-growth 

 of young connective tissue, continuous with and proceeding 

 from the interstitial tissue of the Wolffian body. There 

 can be little doubt that the thickening of the columnar 

 epithelium is brought about by a proliferation of its cor- 

 puscles, and the proliferation itself is due to the influence 

 on the corpuscles of the vascular young connective tissue 

 subjacent to them. While the columnar corpuscles con- 

 stantly proliferate to form the germ epithelial corpuscles 

 from which all the future ova are derived, the rest of the 

 peritoneal chamber becomes lined by a layer of flat 

 epithelium, forming the peritoneal epithelium. 



From the very first appearance of the germ epithelium of 

 the ovary as a distinct structure, processes of the subjacent 

 young connective tissue grow upwards among the corpuscles 

 as the first step in that process of imbedding, whereby the 

 corpuscles become surrounded in meshes of vascular stroma, 

 and ultimately form ova. From its earliest condition till 

 late in the development of the ovary, the germ epithelium 

 cannot be stripped off as a layer from the ovary, because 

 delicate processes of the ovarian stroma are constantly 

 growing up between the corpuscles as fast as they are 

 produced. 



Pfliiger states his opinion that the ovum is simply a peri- 

 toneal epithelial cell. With this statement I cannot 

 altogether agree. Both the ova and the peritoneal cells are 

 undoubtedly evolved from a common ancestral source — the 

 columnar layer of the great peritoneal cavity ; but whilst in 

 one limited region the columnar corpuscles form the germ 

 epithelium and become converted into ova, in the greater 

 part of their distribution they become converted into the 

 endothelium lining the peritoneal cavity. Hence the ovum 

 is no more a modified peritoneal epithelial cell than is the 

 peritoneal epithelial cell a modified ovum. 



From the corpucles of the germ epithelium all the ova are 

 derived. We recognise the germ epithelium by the fact that 

 immediately below it, all round the ovary, are clusters or 

 groups of corpuscles contained in meshes of the ovarian 

 stroma, but under the peritoneal epithelium covering the 

 stalk no such groups are found. 



It is worthy of remark, however, that sometimes under 

 those epithelial corpuscles, which, as it were, form a con- 



