RESPONSES OF YOUNG TOADS 203 



Mature specimens of Bujo americanus will also feign death. 

 The writer has frequently caused toads to exhibit this response 

 by placing them with the back down and in close contact with 

 some solid surface, meanwhile holding them firmly in that posi- 

 tion for approximately thirty seconds more or less. They some- 

 times respond to stimuli of this nature by feigning death for 

 one or more minutes. Near Ann Arbor, Michigan, the leopard 

 frog, Rana pipiens Schreber, is very common. Mature specimens 

 taken in that locality frequently have been made to exhibit the 

 death-feigning response by rough handling and by placing them 

 on their backs on the laboratory table and holding them securely 

 for some time in such a position. Mature toads and frogs exhibit 

 much individual variation in reacting with the death-feigning 

 response. The response is elicited in some animals much more 

 readily than in others. In some instances it seems to be prac- 

 tically impossible to induce the response. The length of the 

 death-feint also varies considerably in different individuals. 

 The death-feigning response is undoubtedly of the same nature 

 as that which Verworn (1898) 3 calls hypnosis. According to 

 this writer specimens of Rana escidenta when turned on their 

 backs, become motionless. Sometimes the hind legs are drawn 

 close to the body, and the eyes are closed. While the animals 

 lie in this position, their muscles are in a condition of "tonic 

 contraction." Hypnotized frogs may assume peculiar attitudes, 

 as if in attempting to right themselves the movements were 

 suddenly inhibited. Verworn (1899, pp. 358-359) in discussing 

 the hypnotic state of frogs makes the following statement : 



"The phenomena of prolonged reflex tone after brief stimulation may- 

 be seen still more clearly in frogs that have been deprived of their cere- 

 brum. If such a frog sitting quietly in the customary squatting attitude 

 be gently stroked by two fingers along the sides of the spinal column, he 

 raises himself upon his extremities by contracting their muscles, and 

 stands, sometimes more than an hour, in this grotesque position." 



According to Verworn (I.e., p. 496) if a frog is seized suddenly 

 and held with a firm grip, and is then placed with its back down 

 the animal remains immobile. A very peculiar contact response 

 on the part of certain toads, Bonibinator ignens and Bonibinator 



3 Beitrage zur Physiologie des Cent ralnervensyst ems I. Die sogenannte Hyp- 

 nose der Thieren. Jena, 1898, pp. iv + 92. This paper was not accessible, but 

 some discussion of it is given in the section on "Hypnotism," Holmes (1907, pp. 

 59, 60, 61), and in a review by Gotch (1898). 



