§ 5 



MODIFICATION IN FOLLICLE 



107 



/?. The calyx nutricius simplex is a special form, adapted 

 to the viviparity of certain fishes. In this case the calyx does 

 not become involuted; the bloodvessels of the follicle form a 

 capillary system through which nourishment (the "embryo- 

 trophe") is conveyed to the ovary-lumen. After the per- 

 formance of this function this calyx also involutes into scar 

 tissue (Fig. 75b). 



Co/yx 



Fig. 75. Modifications of the calyx. 



y. The calyx with retention of the ovum is also an 

 adaptation to the viviparity in fishes, and is at the same time 

 a calyx nutricius; in this case, however, the ovum is fertilised 

 and develops inside the ruptured follicle (Fig. 75c). 



d. The calyx mixtus belongs exceptionally to the same 

 group of calyces nutriciae, differing from the first-named 

 representative in that the more or less expelled granulosa 

 hyperthrophies, and probably also has a certain secretory 

 action. This constitutes as it were a first attempt, on the part 

 of Anamnia, of forming a post-ovulation corpus luteum, and 

 is, therefore, of particular phylogenetic significance (Fig. 



75d). 



£. The calyx cyst may come into existence after the closure 



