EMBRYOLOGY OF CRYPTOBRANCHUS 



111 



In the later stages of the development of the ovary, its walls 

 anastomose by the formation of cross-walls or partitions, divid- 

 ing the ovary into compartments or perhaps pockets; by these 

 cross-walls the course of the inner ovarian membrane is greatly 

 complicated. 



The ovocyte of a female of 26 cm. and younger is apparently 

 a naked cell, possessing no proper membrane. In females with a 



Fig. 18 Cross-section through the ovarian wall of a 26 cm. Cryptobranchus 

 allegheniensis, showing one of the most advanced ovocytes. X 180. n., nucleolus; 

 v., vitelline body; ep., inner epithelial membrane of the ovarian wall. Other 

 lettering as in figs. 13 to IG. 



body length of from 30 to 35 cm. there occurs a rapid development 

 of two non-cellular membranes closely investing the egg within 

 the follicle. The inner of these two membranes exhibits a radial 

 striation and is the zona radiata; at the time of maturation it 

 becomes a simple cell wall to the egg. The outer membrane, 

 clear and homogeneous, is the zona pellucida; it persists as the 

 'vitelline membrane' of the embryo. 



