ii6 follicular derivatives in vertebrates iii 

 § 9. Summary 



To summarize (Table V), we cannot draw a sharp line 

 of distinction either between Anamnia and Amniotes or 

 between Sauropsidans and mammals, since the various fol- 

 licular derivatives overlap phylogenetically. The pre-ovula- 

 tion corpus luteum occurs both in Amphibia and in mam- 

 mals; the atretic follicular derivatives are found in birds and 

 also in reptiles; and the corpus atreticum ruptus is typical 

 of both birds and Monotremata. We may affirm, therefore, 

 that the significance of the calyx and the pre-ovulation corpus 

 luteum from the Cyclostomata to the mammals diminishes 

 in the same proportion as the significance of the post- 

 ovulation corpus luteum and the atresia increases. Where, in 

 this sequence, secretion of oviductin finishes and that of 

 progesterone begins has yet to be investigated. 



