EMBRYOLOGY OF CRYPTOBRANCHUS 89 



together in a single string. At the ends of each string are formed 

 some small but perfect capsules which do not contain eggs. 



The eggs are unpigmented, heavily yolk-laden and strongly 

 telolecithal. 



The nest consists of a submerged cavity under a rock in the bed 

 of the stream. The cavity is sometimes in part the work of the 

 animal. 



Fertilization is external. 



There is a paternal brooding habit, which is manifested from 

 the moment of fertilization. The origin of this habit is problem- 

 atical. 



III. METHODS AND TECHNIQUE 



A. COLLECTION AND CARE OF LIVING MATERIAL 



To insure a convenient supply of adults for various purposes, 

 these were collected before and during the breeding season and 

 placed in a large creek aquarium, constructed of wire netting 

 and placed in shallow water with a gentle current. This arrange- 

 ment of the aquarium afforded abundant aeration; flat stones 

 placed on the bottom provided cover; in general the conditions 

 closely resembled those of the natural environment. The aqua- 

 rium proved of great value as a means of insuring a supply of 

 adults for use at frequent intervals in securing material for the 

 study of ovogenesis, maturation, fertilization and the early cleav- 

 age stages. 



Artificial fertilization was often resorted to in order to control 

 the time of fertilization for the study of fertilization and early 

 cleavage stages, and occasionally eggs were used that had been 

 deposited and fertilized by specimens in captivity; but the greater 

 part of the material used for the study of the development was 

 obtained from the nests of the animals in their natural environ- 

 ment. 



At first the problem of keeping the eggs alive in a favorable 

 environment while studying their development promised some 

 difficulty. Early attempts to keep the eggs in creek aquaria 

 met with disastrous failure through the attacks of water-mould. 

 The method finally employed was to keep the eggs in shallow 



