4O The Dancing Mouse 



of activity is an expression of the habits of the mouse race 

 rather than of the immediate influence of any environmental 

 condition. At some time in the history of the dancer light 

 probably did have an influence upon the period of activity; 

 but at present, as a result of the persistence of a well-estab- 

 lished racial tendency, the periodicity of dancing depends to 

 a greater extent upon internal than upon external conditions. 

 During its hours of quiescence it is possible to arouse the 

 dancer and cause it to whirl more or less vigorously by stimu- 

 lating it strongly with intense light, a weak electric current, 

 or by placing two individuals which are strangers to one 

 another in the same cage; but the dancing thus induced is 

 seldom as rapid, varied, or as long-continued as that which 

 is characteristic of the evening hours. 



One of the most interesting results of this study of the 

 direction of turning, from the observer's point of view, is 

 the demonstration of the fact that the truth concerning even 

 so simple a matter as this can be discovered only by long and 

 careful observation. The casual observer of the dancer gets 

 an impression that it turns to the left more often than to the 

 right ; he verifies his observation a few times and then asserts 

 with confidence that such is the truth about turning. That 

 such a method of getting knowledge of the behavior of the ani- 

 mal is worse than valueless is clear in the light of the results 

 of the systematic observations which have just been reported. 

 But, however important the progress which we may have 

 made by means of systematic observation of the phenomenon 

 of turning, it must not for one moment be supposed that the 

 whole truth has been discovered. Continued observation 

 will undoubtedly reveal other important facts concerning 

 circling, whirling, and the periodicity of dancing, not to men- 

 tion the inheritance of peculiarities of dancing and the sig- 

 nificance of the various forms of activity. 



