PRELIMINARY REPORT ON THE EMBRYOLOGY OF 

 CRYPTOBRANCHUS ALLEGHENIENSIS. 1 



BERTRAM G. SMITH. 



Although the eggs of the hellbender, Cryptobranchus (JMcno- 

 pojnd) allegheniemiS) have been eagerly searched for by embry- 

 ologists, a few unfertilized eggs only have hitherto been obtained. 

 Aside from a brief description of an embryo in an advanced stage 

 by McGregor ('96), there is no record of any observations on 

 the development. The manner in which the eggs are fertilized 

 has not been described. 



This gap in our knowledge of comparative embryology is 

 serious, particularly as very little is known about the develop- 

 ment of the two other members of the family - Amphiumidae : 

 the giant salamander of Japan, Cryptobranchus japonicus (Megalo- 

 batrachus maximus Schlegel), and the American Auiplnuina 

 means. 



During the early part of September, 1905, in northwestern 

 Pennsylvania, I was so fortunate as to obtain fertilized eggs of 

 Cryptobranchus allegheniensis in abundance, both from specimens 

 in captivity and from the natural habitat of the animal. 



I. THE SEXUAL ELEMENTS. 



A. The Egg. The egg proper is perfectly spherical when 

 fresh, about the size of a large pea, and bright yellow in color 

 a rather deep yellow at the lower pole, grading to a pale yellow 

 at the upper. There is no black pigment such as is found in 

 the eggs of most amphibians. A very thin transparent mem- 

 brane, the vitelline membrane, quite inconspicuous in fresh material, 

 closely invests the egg. Each egg, with its vitelline membrane, 

 floats in a clear fluid within a hollow sphere or capsule about 

 the size of a large grape, formed by the thick gelatinous outer 



1 Contributions from the Zoological Laboratory of the University of Michigan, No. 

 105. 



2 Gadow's classification is followed ('01). 



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