110 



BERTRAM G. SMITH 



number of nuclei keeps pace with the increase in extent. In a 

 35 cm. female (see figs. 21 and 22), the nuclei of the follicular 

 membrane are the most numerous and least flattened; those of the 

 cyst membrane and inner ovarian membrane are both decidedly 

 flattened. Somewhat rarely, the cyst membrane is ruptured 

 by the expansion of the ovocyte. According to King ('08) in 

 Bufo the rupture of the cyst membrane takes place regularly at an 

 early stage. 



Fig. 17 Cross-section through the ovarian wall of a 9 cm. larva of Cryptobran- 

 chus allegheniensis, showing one of the most advanced ovocytes. X 300. Letter- 

 ing as in the preceding figures. 



The ovocyte in the advanced growth stage is thus surrounded 

 by a single-layered follicle, suspended in a flask-shaped two- 

 layered sac of which the inner layer is the cyst membrane, the 

 outer layer is the inner epithelial membrane of the ovarian wall. 

 In a broader sense, the entire three-layered structure may be 

 called a follicle, and the neck of the flask-shaped sac may be called 

 the stalk of the follicle. This triple-layered wall persists without 

 any radical change in structure up to the time of maturation. 



