REACTIONS OF CRVPTOBRANCH US AND NECTL'RUS. 97 



Parker ('05) thinks that the sensitiveness to light of young 

 lamprey eels is due to stimulation of the ends of the spinal nerves 

 in the skin ; this may be the case here also. He found ('05) 

 that in the ammocoer.es, as in Cryptobranchus, the tail is the most 

 sensitive part of the body, the response being negative. In the 

 frog, on the other hand, he found ('03) the reaction to be positive. 

 Just as it is of value to the young lamprey, on account of its 

 burrowing habits, to have a tail that is sensitive to light, so is the 

 sensitive tail probably of value to the giant salamander because 

 of the animal's habit of concealing itself under objects in its native 

 haunts. The fact, as I have already shown ('05), that the eyes 

 of this animal are probably not very sensitive, may have some- 

 thin to do with the unusual sensitiveness of the tail. 





THERMIC REACTIONS OF CRYPTOBRANCHUS. 



The temperature experiments were made upon four adult speci- 

 mens, the same ones that were used in the light experiments. 



When taken from their tank, where the water was at 18 

 C., and put into water at 33 none of the four animals 

 showed any signs of being aware of the change of medium ; the 

 same negative results were noted when they were changed from 

 water at 5 to water at 26. On one occasion, however, they 

 showed slight signs of discomfort when put from water at 14 

 into water at 26. 



Removal of the animals from water at either 18 or 26 to 

 water at 42 resulted in the most violent struggles, beginning 

 after an immersion of two or three seconds and lasting, usually, for 

 a minute or more, or until the animal was completely exhausted. 

 The violence of these struggles was quite remarkable, though 

 less marked in some cases than in others. In some instances the 

 struggles continued until the animal was completely exhausted 

 and turned belly side up as though dead ; in other cases the 

 struggles gradually ceased until the animal lay quietly in the 

 warm water. Two of the animals died soon after the experi- 

 ments, probably as the result of their experiences, as they had 

 seemed perfectly healthy before. 



Removal from water at 26 to water at 5, or from water at 

 1 8 to water o caused no reaction, although, in the former case, 



