EMBRYOLOGY OF CRYPTOBRANCHUS 63 



In the case of Cryptobranchus the difficulty in finding embryo- 

 logical material seems to have been - enhanced by the unusual 

 breeding season of the animal; the eggs are laid in the fall, while 

 most amphibia spawn in the spring. Townsend ('82) published 

 a general description of some fertilized eggs which he states were 

 deposited in August. McGregor ('96) described very briefly an 

 embryo 16 mm. in length, and ('99) stated that the eggs are depos- 

 ited in August and September. Yet the information thus acquired 

 in regard to the time of spawning seems not to have become gener- 

 ally known to others who were searching for the eggs. A sugges- 

 tion might have been obtained from Sasaki's ('87) observation 

 that the Japanese 'giant salamander,' Cryptobranchus japoni- 

 cus (Megalobatrachus maximus Schlegel), deposits its eggs in 

 August; but this also seems to have been overlooked. Reese 

 ('04) succeeded in obtaining some unfertilized eggs, of which he 

 gave the first detailed description. 



The embryological record for Cryptobranchus allegheniensis 

 remained almost a blank until 1906, when I published a prelimi- 

 nary report containing, besides a description of the sexual ele- 

 ments, a brief account of the external development during the 

 cleavage stages. A later contribution (Smith, '07) , devoted chiefly 

 to the habits, more particularly the breeding habits, included a 

 very general account of the life history. 



From a phylogenetic point of view great interest attaches to 

 the amphibia; there is no doubt that they lie close to the extinct 

 ancestral stock of the highest forms of vertebrate life. Concern- 

 ing the origin of the amphibia themselves Kingsley ('99) says: 

 ''All the facts of structure and development go to show that the 

 amphibia have arisen from the crossopterygian ganoids, and that 

 existing groups have descended from the stegocephali, each by 

 its own line of ancestry." But when we inquire further, and 

 attempt to trace more particularly the origin of any group of exist- 

 ing amphibia from an extinct form exhibiting affinities to the 

 crossopterj^gii, we are landed at once in the midst of uncertain- 

 ties. Confining our attention to the urodeles, we are confronted 

 with the difficult question of the phylogenetic relationships of 

 the different members of this group. The problem will be more 



