22 THE PLxVY OF ANIMALS. 



course. But when this need is not present, as is the 

 case in our examjDle, she still leaps after the ball; and 

 only when disabled through utter fatigue would the 

 cat fail to obey the impulse. The physiological condi- 

 tions that lead a young animal to play at hunting need 

 not be any other than those which enable an adult ani- 

 mal to pursue its natural prey. 



If, therefore, these facts lead us to expect to find 

 the chief problems of play in our conception of instinct, 

 they also force upon us a consideration of the great bio- 

 logical significance of play. For even if I should not 

 succeed in convincing the reader that superabundance of 

 nerve energy is not even a conditio sine qua non, but 

 rather only a particularly favourable condition for play, 

 I have still every right to maintain that the Schiller- 

 Spencer theory is unsatisfactory; for while it attempts, 

 it is true, to make clear the physiological conditions of 

 play, this theory has notliing to say about its great bio- 

 logical significance. According to it, play would be only 

 an accidental accompaniment of organic development. 

 Tor the advance toward perfection, due to the struggle 

 for existence, brings it about that the more highly de- 

 veloped animals have less to do than their powers are 

 competent for. Opposed to this xiew is the very gen- 

 eral conviction among those who study animals that 

 the play of young animals especially has a clearly defined 

 biological end — namely, the preparation of the animal 

 for its particular life activities. I have heard this ex- 

 planation of play given in similar terms by foresters and 

 by zoological specialists. Thus Paul Souriau says, in the 

 article already referred to : " The necessity for move- 

 ment is especially great in youth, because the young ani- 

 mal must try all the movements that he has to make 

 later, and also exercise his muscles and joints to de- 



