194 BERTRAM G. SMITH. 



under side of a large rock about fifteen or twenty empty egg 

 capsules of Nectums, all in good condition. At the distal end 

 of each capsule was a large round hole through which the embryo 

 had escaped. 



THE LARV.E. 



i. The Embryo at the Time of Hatching. Fig. 2 is from a 

 photograph of an embryo of Necturus obtained from Lake Mon- 

 ona on July 5, 1910. This embryo was apparently ready to 

 hatch, since nearly all the other embryos in the nest had already 

 hatched out. 



FIG. 2. Necturus embryo ready to hatch, killed in Tellyesnicky's fluid and pre- 

 served in formalin, July 5, 1910. (X 3%-) From Lake Monona. 



The embryos of Necturus are hatched in a less advanced stage 

 of development than is the case with Cryptobranchus (see Smith, 

 '07, Fig. 9); but in Cryptobranchus at least there is considerable 

 variation in the time of hatching and the figure referred to repre- 

 sents one of the more advanced of the newly-hatched embryos, 

 hence the difference may be less than the figures indicate. 

 Necturus is hatched in water of a much higher temperature than 

 is the case with Cryptobranchus, and this would naturally tend 

 to soften the gelatinous envelope and aid in the early escape of 

 the embryo. 



In Necturus the large yolk content at the time of hatching is 

 even more noteworthy than in Cryptobranchus. Though set 



