RHYTHMS IN BEHAVIOR 155 



starfish was prevented from using these rays and was al- 

 lowed to turn only on those rays which it was least prone 

 to employ. If, after a number of trials, the starfish came 

 to employ the latter most frequently it would be fair to 

 conclude that the animal had acquired a new habit of turn- 

 ing. After one or two days' training most of the individ- 

 uals experimented on came to turn upon rays which they 

 were at first disinclined to use. The effect of the training 

 was not manifest, however, after twenty-four hours. In 

 specimens "trained" for a week or more the habit formed 

 persists, according to Jennings, for twenty-four hours or 

 even several days. The data obtained on this subject 

 were not extensive, and when we consider several sources 

 of error involved, not entirely convincing; further work 

 would be necessary before we could safely conclude that 

 starfish form lasting habits. 



How shall habit formation hi the starfish be interpreted? 

 Moore has shown that irritation of an arm inhibits its ac- 

 tivity and causes the starfish to use other arms in the right- 

 ing movements; and the operation of handling the animal 

 during its "lessons" so as to prevent a certain arm from 

 being used might produce a similar effect. There is no evi- 

 dence that there is any element of association involved, and 

 it is not quite clear whether the basis of the habit lies in 

 the nervous system or in other parts of the organization. 



RHYTHMS IN BEHAVIOR 



Georges Bohn has the merit of having discovered that 

 the rhythms of activity which are produced in many animals 

 by regularly recurring external conditions such as the alter- 

 nation of day and night and the periods of low and high tide 

 may persist for some time after the animals are withdrawn 

 from the direct influence of the outer periodic changes. 



