RESPONSES OF YOUNG TOADS 201 



response of hibernating frogs. Dickerson (I.e., p. 71) has 

 observed the tendency of young toads, Bufo americanus Le 

 Conte, to crawl "under stones and chips, in the cracks of board- 

 walks or under the protecting cover of leaves and grasses." The 

 young toads to which she referred had left the water just re- 

 cently and were therefore very delicate creatures, and they 

 remained during the daytime in such protected situations as 

 have been mentioned. So that while these responses are prob- 

 ably due in part to contact stimuli, yet other stimuli also such 

 as light and temperature undoubtedly have considerable influ- 

 ence in bringing them about. The burrowing response of young 

 spadefoot toads, Scaphiopus holbrookii Harlan, exhibits itself 

 early in the life of the individual (Dickerson, I.e., p. 56), and 

 is in part at least a response to contact. According to Holmes 

 (I.e., p. 351) there is a tendency for frogs and toads to crawl 

 under stones and to place themselves between objects. In such 

 positions they remain quiet. This propensity to move into 

 such situations is more pronounced in the case of toads. He 

 considers such responses to be of a thigmotactic nature, although 

 from his discussion it may be inferred that at times light also 

 plays some role. 



Considerable care was used in handling the young toads dur- 

 ing the experiments with light. They were removed from the 

 aquarium jar and placed in the experimentation trough by 

 hand. In order that such contact should modify the response 

 to light as little as possible, the toads were left undisturbed for 

 approximately fifteen minutes before being subjected to the 

 photic stimuli of the experiment. Should the toads while being 

 transferred from one vessel to another be handled with undue 

 pressure and roughness, they sometimes assume an immobile 

 state. As this response was a somewhat unfamiliar one to the 

 writer a number of observations were recorded concerning it. 



Frequently when young specimens of Bufo americanus are 

 handled, the contact stimulus causes them to become motionless ; 

 they react with the death-feigning response. Certainly they 

 assume an attitude which is comparable to that assumed by 

 many Arthropods when they are said to feign death. The legs 

 are drawn up closely against the body and they assume a more 

 or less rigid condition, the animal remaining motionless. Some- 

 times a toad lies so absolutely quiet that even the respiratory 



