Behavior: Dance Movements 39 



derance of left whirlers indicated above is due to a strong 

 tendency to turn to the left which was exhibited by the in- 

 dividuals of one line of descent. 



The tendency of the dancer's activity to increase in amount 

 toward evening, which the results of Tables 2, 3, and 4 ex- 

 hibit, demands further consideration. Haacke (7 p. 337) and 

 Kishi (21 p. 458) agree that the dancing is most vigorous in 

 the evening; but Alexander and Kreidl (i p. 544) assert, on 

 the contrary, that the whirling of the individuals which they 

 observed bore no definite relation to the time of day and 

 apparently was not influenced in intensity thereby. Since the 

 results of my own observations contradict many of the state- 

 ments made by the latter authors, I suspect that they may 

 not have watched their animals long enough to discover the 

 truth. The systematic records which I have kept indicate 

 that the mice remain quietly in their nests during the greater 

 part of the day, unless they are disturbed or come out to 

 obtain food. Toward dusk they emerge and dance with vary- 

 ing intensity for several hours. I have seldom discovered one 

 of them outside the nest between midnight and daylight. The 

 period of greatest activity is between 5 and 10 o'clock P.M. 



Zoth states that he has observed the adult dancer whirl 

 79 times without an instant's interruption, and I have counted 

 as many as no whirls. It seems rather absurd to say that 

 an animal which can do this is weak. Evidently the dancer 

 is exceptionally strong in certain respects, although it may be 

 weak in others. Such general statements as are usually 

 made fail to do justice to the facts. 



The supposition that light determines the periodicity 

 of dancing is not borne out by my observations, for I have 

 found that the animals continue to dance most vigorously 

 toward evening, even when they are kept in a room which is 

 constantly illuminated. In all probability the periodicity 



