OVARIES IN TELEOSTEAN AND ELASMOBEANCH FllSHES. 203 



have described above^ but it is never formed in the ruptured 

 follicle. Also the "Narbengewebe " iu question is a product 

 of the follicular epithelium^ not of the connective tissue as 

 Stuhlmann imagined. 



In figs. 24 — 26 I have indicated how an ovigerous pouch 

 from which an egg has escaped is converted into a villus. 

 Fig. 24 is a longitudinal section of a recently ruptured pouch 

 (August 19th). Figs. 25 and 26 are sections, longitudinal 

 and transverse respectively, of villi from a pregnant ovary 

 in February. In this ovary advanced " embryos," almost 

 ready for birth, were present. The conversion of an ovige- 

 rous pouch into a "villus" is brought about as follows : — The 

 pouch, which at the time of rupture is a pear-shaped and sub- 

 sessile vesicle (fig. 24), elongates to ultimately about three 

 times its original size ; it is now a long-stalked clavate 

 structure (fig. 24). At the same time the egg cavity collapses 

 gradually, and closes up by a doubling iu and apposition of 

 its walls — the theca folliculi. This layer becomes very 

 thick after the rupture of the follicle, and the blood-vessels iu 

 it (arteries) and in the subepithelial stroma (veins) become 

 greatly enlarged. The follicular epithelium undergoes no 

 further development beyond a slight hypertrophy by simple 

 enlargement of its cells; it ultimately degenerates into a few 

 yellow granules. A similar hypertrophied condition of the 

 follicular epithelial cells and nuclei was noted above as 

 characterising certain follicles in which the egg is about to 

 degenerate. The cause of this enlargement of the cells is 

 probably the same in both cases ; the egg being functionless, 

 as in the one case, or gone, as in the other, the nutriment 

 passing from the blood to the cells of the follicular epithelium 

 is no longer rapidly absorbed as it would be if a functional 

 egg were present, but accumulates in the cells, which accord- 

 ingly become turgid. This turgidity may bring about the 

 observed hypertrophy of these cells. 



Growth, by simple hypertrophy, of the cells of the follicular 

 epithelium is stated by vSobotta (1895) to characterise the 

 formation of the corpus luteum in the mouse; and Marshall 



