OVARIES IN TELEOSTEAN AND ELASMOBRANCH FISHES. 189 



are fixed in the membrane. In other sections, again, the 

 vitellus, together with the zonoid layer, has shrunk away 

 from the egg membrane, while the follicular epithelium is 

 closely applied to the latter. At such places delicate fibrils 

 may occasionally be seen stretching across the space, to be 

 inserted in the egg membrane. Although no processes were 

 seen actually to traverse the substance of the egg membrane, 

 it is difficult to account for the appearances just described 

 except on the assumption that the membrane is penetrated by 

 the processes of the follicular cells. In Chimajra the demon- 

 stration of processes of these cells traversing the (modified) 

 egg membrane is complete (fig. 30). 



Chimgera differs from Spin ax in regard to the condition 

 of the follicular epithelium in immature egg. In Spin ax the 

 follicular epithelium is a single layer of cells. Hat in the 

 smaller eggs and over the animal pole of the larger ova, but 

 more or less columnar over the rest of the surface, and espe- 

 cially high at the vegetable pole (fig. 19). Spinax resembles 

 Acanthias vulgaris, Scymnus licliia, Heptanchus 

 cinereus, and Mustelus laevis^ in the persistent single- 

 ayered condition of the follicular epithelium. Chimasra 

 agrees with Raia, Scyllium (Balfour), Torpedo (Schultze), 

 Myliobatis, Trygon (Giacomini), in having a thick follicu- 

 lar epithelium with two kinds of cells — large specialised 

 " nuti-itive " cells and small indifferent cells. The same 

 differentiation of the cells in the follicular epithelium is found 

 in reptiles. The nutritive cells degenerate and disappear 

 before the maturation of the egg, when the follicular epithe- 

 lium reverts to the single-layered condition. 



Giacomini (1896) gives a brief description of the follicle of 

 C him sera. He mentions that the epithelium consists of 

 large cells, intercalated among which are small cylindrical 

 cells ; that the large cells possess a vesicular nucleus ; that 

 they are provided with fine processes directed against the 

 vitelline membrane. 



In the very young follicles of C him sera the follicular epi- 



* Giacomini, 1896, p. 230. Spiuax. was not investigated hy tliis author. 



