300 Journal of Comparative Neurology and Psychology. 



changes. The green frog is stimulated by sounds as low as 50 

 vibrations per second. No experimental tests were made with 

 lower sounds. For the purpose of determining the upper limit 

 of audibleness tests were made with Galton and Appunn whis- 

 tles. The tactual reflex was again employed as a means of 

 testing the influence of sound. The tests, like those of the 

 previous section of the paper, were made during the winter and 

 responses to both tactual and auditory stimuli were obtained 

 much more regularly with females than with males. A suffi- 

 cient number of reactions have been recorded for males, howev- 

 er, to prove that they are influenced by sounds as high as 

 10,000 vibrations per second, as are the females also. The fol- 

 lowing series of averages for a female is indicative of the nature 

 of the results of these tests : 



Green frog Galton whistle Amount of tactual reaction Amount of auditory-tac- 

 female vibration rate Average of twenty reactions tual reaction in each case. 



Series I 5, 000 2.80 mm. 4.65 mm_ 



•' II 8,000 2.60 " 5.45 " 



" III 10,000 2.10 '• 4.20 " 



" IV Puff of air alone 2.45 " 2. 30 " 



Series IV serves as a control on the influence of the sound 

 of escaping air which accompanies the tone of the whistle. Its 

 result indicates that the tone is the effective stimulus in the pre- 

 ceding series. 



Similar results obtained by the use of the Appunn whistles 

 prove that up to 10,000 vibrations per second the frog is stimu- 

 lated by sound. With neither the Galton nor the Appunn whistles 

 was evidence of reaction to sounds of higher vibration rate ob- 

 tained. We may therefore conclude, until further investigation 

 by more satisfactory methods is available, that the green frog 

 is influenced by sounds ranging in rate of vibration from 50 to 

 10,000 per second. It should be noted, however, that neither 

 the upper nor the lower limit of audition has been accurately 

 determined by these experiments. 



