152 BERTRAM G. SMITH. 



He found a viscid substance containing spermatozoa exuding 

 from the vent of a male specimen in May (April, according to 

 his earlier paper), and concluded that this month is the natural 

 season for fertilization. 



The occurrence of the breeding season of Cryptobranchus in 

 the fall is in marked contrast to the habits of nearly all other 

 Urodeles, since they lay their eggs in the spring. While the sig- 

 nificance of this unusual breeding season is not readily apparent, 

 it is, in the case of C. allegheniensis, in at least one respect 

 adaptive. The animal is an inhabitant of streams that during 

 spring and early summer are subject to frequent and destructive 

 freshets, which would probably be disastrous to the development 

 of eggs like those of Cryptobranchus. During late summer and 

 fall the streams are shallow and the water comparatively quiet ; 

 floods are of rare occurrence. These factors do not affect the 

 other amphibians of the region in the same way, since they are 

 inhabitants of ponds not seriously disturbed by floods, and on 

 account of the more abundant rainfall better adapted for breed- 

 ing-grounds in the spring than later in the year. There is every 

 reason to believe that these climatic conditions have been of lone 



o 



duration. Probably the same conditions prevail with regard to 

 C.japonicus, which is an inhabitant of mountain streams similar 

 to those in which C. allegheniensis occurs. In this connection 

 Professor Jacob Reighard informs me that the increase of spring 

 freshets in Michigan during recent years, aided no doubt by other 

 effects of lumbering operations, has nearly caused the extinction 

 of the grayling, a fish that breeds in the spring, and was formerly 

 abundant ; the trout, which breeds in the fall, now thrives in the 

 same streams. These facts indicate the selective value of the fac- 

 tors mentioned, and support the view taken with regard to 

 Cryptobranchus. 



C. Breeding Habitat. - - Eggs of Cryptobranchus were found in 

 shallow water in what had once been the main channel of a laree 



o 



stream, but through which now only a portion of the water, sep- 

 arated from the main channel by an island, flows. This old 

 river channel is extremely rocky, with a considerable incline, so 

 that the shallow water alternately forms pools and rapids. 

 Judging from the number of specimens seen, the locality is a 



