14 BERTRAM G. SMITH. 



times makes a rather loud crackling sound, like that produced by 

 boys who snap the joints of their fingers. The noise seems to 

 come from the articulations of the vertebrae. 



When tightly squeezed about the neck, the hellbender some- 

 times utters a shrill cry, perhaps due to the involuntary expulsion 

 of air from the lungs. 



Reaction to Light. — As previously stated, Cryptobranchus 

 avoids the light. Like its thigmotactic response, this reaction 

 is an important factor in its customary mode of life, since it usually 

 seeks by day the cover of rocks where, concealed from possible 

 enemies, it lies in wait for prey. Specimens confined in the labor- 

 atory are nocturnal in their activities, and during the day seek 

 the darkest corner of the aquarium. According to Reese ('06), 

 the tail is much more sensitive to light than the head or the 

 middle part of the body. This may partly account for the favor- 

 ite position of the animal — lying under a rock with only the fore 

 part of the head exposed. 



B. Breeding Habits. 



Sexual Differences. — The adult male may be recognized 

 (Reese, '04) by the presence of a swollen glandular ring or ridge 

 of tissue about the opening of the cloaca. This is especially 

 prominent in the breeding season, but may be recognized before 

 the breeding season begins. 



Females in the breeding season may be distinguished by the 

 swollen appearance of the abdomen. As the egg-laying season 

 approaches the eggs collect in the uteri, and when a ripe female 

 is held in a vertical position with head uppermost, the lower 

 portion of the abdomen sags and bulges out. 



Females were found to be quite scarce or perhaps inaccessible 

 as compared with the males. The ratio in those captured was 

 about 1 : 8. 



Breeding Season. — As the time of the beginning of the breed- 

 ing season was not accurately known, on August ill examined 

 the reproductive tract of a newly captured male 34 cm. in length. 

 The vasa deferentia were found to be contracted, about 2 mm. 

 in diameter, and almost empty, containing only a very few sperma- 

 tozoa, and these at the upper end. The spermatozoa were immo- 

 tile. In the testes very few spermatozoa were mature. 



