EMBRYOLOGY OF CRYPTOBRANCHUS 71 



4- The eggs 



{a). General history of the eggs and their enoelopes before the time 

 of spawning. In an adult female of average size about 450 

 eggs are matured each season — 225 from each ovary. In general 

 the number is greater in the larger and presumably older females 

 than in the smaller ones. At the approach of the breeding sea- 

 son the eggs which are about to become mature are readily dis- 

 tinguishable from the others by their much greater size and yolk 

 content. The liberation of these eggs from the ovary and their 

 passage down the oviduct takes place shortly before spawning. 

 The exact date varies considerably in different individuals; for 

 a week or ten days after the first cases of spawning, females may 

 be found with mature eggs all still in place in the ovaries. The 

 process of liberation of the eggs and their passage down the ovi- 

 duct, once begun, must be accomplished with considerable rapid- 

 ity; for out of more than a hundred females opened and examined 

 during the breeding season in the course of several years, only 

 four have been found in which the process was actually taking 

 place. This state of affairs is in marked contrast to the condi- 

 tion in Bufo, where according to King ('05) the great majority 

 of specimens collected soon after they had emerged from their 

 hibernation contained eggs free in the body cavity. In three 

 out of the four cases above mentioned for Cryptobranchus, eggs 

 were found along the entire route: some still in place in the ovary; 

 some free in the body cavity, for the most part collected at its 

 anterior end, near the opening of the oviduct; others forming a 

 procession down the oviduct; the remainder aggregated in the 

 uterus. In the fourth case, the ripening eggs were found only 

 in the body cavity, oviduct and uterus. The process takes place 

 on the two sides of the body simultaneously. 



During their passage down the oviduct the eggs receive their 

 gelatinous outer envelopes, the product of the oviduct. At the 

 upper end of the oviduct, the eggs collect in masses; a httle further 

 down, they are arranged in a solid row. In these parts of the 

 oviduct the covering is absent or just beginning; the eggs are very 

 soft, and elongated by pressure of the walls of the oviduct. In 



