The Sense of Hearing 



89 



TABLE 5 

 PERIOD OF AUDITORY REACTION IN YOUNG DANCERS 



Certain of the litters tested responded definitely to sounds, 

 others gave no sign of hearing at any time during the first 

 four weeks of life. Of the twelve litters for which the re- 

 sults of auditory tests are presented in Table 5, eight evi- 

 dently passed through an auditory period. It is important 

 to note that all except one of these were the offspring of 

 Nos. 151 and 152, or of their descendants Nos. 410 and 415 

 and Nos. 420 and 425. In fact every one of the litters in 

 this line of descent which I have tested, and they now num- 

 ber fifteen, has given indications of auditory sensitiveness. 

 And, on the other hand, only in a single instance have the 

 litters born of Nos. 210 and 215, or of their descendants, 

 given evidence of ability to hear. 



These two distinct lines of descent may be referred to 

 hereafter as the 400 and the 200 lines. I have observed 

 several important differences between the individuals of these 



