298 Journal of Comparative Neurology and Psychology, 



dently the seasonal condition of the animal is an important mat- 

 ter to consider in studies of audition. 



The experiments included tests under three conditions: 

 I. When the tympanum was exposed fully to air, although the 

 body was submerged up to the level of the eardrum ; 2. When 

 the tympanum was half under water, the head and nares being 

 in air ; 3. When the frog was submerged to a depth of 4 cm. 



The results prove beyond doubt that sounds made in the 

 air stimulate frogs when their tympana are under water. Furth- 

 ermore, there is evidence that sounds stimulate the green frog 

 even when it is totally submerged to a depth of four centime- 

 ters. I cannot better describe these results than by giving the 

 sample series of Table III. 



Although the amount of reaction under the conditions of 

 these experiments is small, the difference between the tactual 

 and the auditory-tactual is sufficiently great to establish the 

 frog's ability to hear under water. 



The averages for ten reactions of another female under 

 four sets of external conditions follow : 



Condition Amount of reaction to Amount of reaction to the 



tactual stimulus alone. auditory-tactual alone. 



Tympanum in air 2.0 mm. 16.4 mm. 



•' half under water .9 " 13.5 " 



" 1 cm. under water 1. 3 " 3.5 " 



" 4 cm. under water .5 " I. a " 



With several other individuals reactions were obtained 

 which just as clearly indicated audition under water. We may 

 therefore conclude that the green frog can hear both in air and 

 under water. 



There is some evidence that the reaction to sound is greats 

 est when the tympanum is half submerged. 



V. The Range of Hearing. 



By one or another of the methods of experimentation 

 already described the value of the following sounds as auditory 

 stimuli for the frog has been demonstrated during the course of 

 this investigation. The croaking of green, leopard and bull- 

 frogs ; splashing of water ; pistol explosions ; tuning forks rang- 



