1 68 Correspondence 



auditory. Experiments described in the remainder of the paper proved to my 

 satisfaction "that the reactions with which we have to deal in this investigation are 

 due to stimulation of certain sense organs of the ear, and that the use of the word 

 hearing in connection with them is appropriate." 



Dr. Edinger's criticisms call attention to several important neurological facts 

 which must be taken into account by the student of animal behavior, and suggest 

 possible striking differences in the sense processes of animals. Despite the misun- 

 derstanding of my conclusions, I greatly appreciate and have profited much by 

 Dr. Edinger's kindly criticism and general approval of my work. 



With reference to Prof. Boettcher's comments I wish to say that the state- 

 ments of my paper were meant to apply only to the three species of frog studied 

 R. clamitans, R. catesbiana and R. pipiens. I, too, can confirm his observations 

 concerning the reactions of tree-frogs, but I have still to see or hear of locomotor 

 reactions by frogs in response to sounds. I do not doubt, however, that they occur 

 in many species, and I hope observations of such reactions may soon be put on 

 record. 



ROBERT M. YERKES 



