78 The Dancing Mouse 



to determine the direction whence comes a sound, yet usually 

 the mouse gives no other sign of hearing. That the absence 

 of ordinary reactions to sounds is due to deafness, Kishi, like 

 Panse, is led to doubt because his anatomical studies have 

 not revealed any defects in the organs of hearing which would 

 seem to indicate the lack of this sense. 



This historical survey of the problem of hearing has 

 brought out a few important facts. No one of the several 

 investigators of the subject, with the exception of Cyon, is 

 certain that the dancer can hear, and no one of them, with 

 the exception of Rawitz, is certain that it cannot hear ! 

 Cyon almost certainly observed two kinds of dancing mice. 

 Those of his dancers which exhibited exceptional ability to 

 climb in the vertical direction and which also gave good evi- 

 dence of hearing certain sounds may have been hybrids result- 

 ing from the crossing of the dancer with a common mouse, or 

 they may have been exceptional specimens of the true dancer 

 variety. A third possibility is suggested by Rawitz's belief 

 in the ability of the young dancer to hear. Cyon's positive 

 results may have been obtained with immature individuals. 

 I am strongly inclined to believe that Cyon did observe two 

 types of dancer, and to accept his statement that some of 

 the mice could hear, whereas others could not. It is evident, 

 in the light of our examination of the experimental results 

 thus far obtained by other investigators, that neither the 

 total lack of sensitiveness to sounds in the adult nor the 

 presence of such sensitiveness in the young dancer has been 

 satisfactorily proved. 



I shall now report in detail the results of my own study 

 of the sense of hearing in the dancer As the behavior of 

 the young differs greatly from that of the adult, by which is 

 meant the sexually mature animal, I shall present first the 

 results of my experiments with adults and later, in contrast, 



