Structural Peculiarities and Behavior 61 



The above structural deviations of the ear of the dancer 

 from that of the common mouse may be considered as pri- 

 mary or secondary according as they are inherited or acquired. 

 Since, according to Alexander and Kreidl, the dancers' 

 peculiarities of behavior and deafness are directly and uni- 

 formly inherited, it is obvious that certain primary structural 

 deviations must serve as a basis for these functional facts. 

 But it is equally clear, in the opinion of Alexander and Kreidl 

 (2 p. 536), that other structural peculiarities of the dancer 

 are the result of the primary changes, and in no way the 

 conditions for either the dancing or the deafness. These 

 authors feel confident that the facts of behavior which are to 

 be accounted for are almost certainly due to the pathological 

 changes which they have discovered in the nerves, ganglia, 

 and especially in the peripheral nerve endings of the ear of 

 the mouse (2 p. 537). 



It is further claimed by Alexander and Kreidl that there 

 are very marked individual differences among the dancers 

 in the structure of the ear. In some cases the otoliths and 

 the sensory hairs are lacking; in others, they are present 

 in the state of development in which they are found in other 

 varieties of mouse. Sometimes the cochlea is much reduced 

 in size ; at other times it is found to be of normal size (2 p. 

 538). These variations in structure, if they really exist, 

 go far toward justifying the tendency of Cyon and Alexander 

 and Kreidl, as well as many other investigators, to regard 

 the dancer as abnormal or even pathological. 



The functions of the ear as at present known to the com- 

 parative physiologist are grouped as the acoustic and the 

 non-acoustic. The cochlea is supposed on very good grounds 

 to have to do with the acoustic functions, and the organs of 

 the semicircular canals on equally good evidence are thought 

 to have to do with such of the non-acoustic functions as 



