220 THE BIOLOGY OF THE SEASONS 



purposes of clearness, we shall leave out of consideration 

 at present anything that might be interpreted as love-play 

 or courting-play, and keep mainly to the play of young 

 animals. 



There are two main theories as to the play of young 

 animals, and the first is that play is an expression of over- 

 flowing vigour, energy, and animal spirits ; that it is the 

 byplay of vigour. This view was first clearly stated by 

 Schiller ; it was long afterwards elaborated by Herbert 

 Spencer a strange contrast of champions. 



This theory is simple ; but it is too simple, and it breaks 

 down badly. No doubt the young creature is an overflowing 

 well of energy ; but even the tired animal or child will 

 turn in a moment from fatigue to play. Moreover, the 

 theory does not in the least explain the characteristic forms of 

 play in different animals. In fact, the theory only states 

 one of the internal or physiological conditions of play 

 there must be some energy to spare. 



Schiller's theory of play was re-expressed, as we have 

 said, by Herbert Spencer ; but he, feeling its inadequacy, 

 eked it out by laying emphasis on imitation. The cause, 

 he said, is superfluous energy ; imitation defines the channel 

 of expression. The youngsters mimic in play what they 

 see their seniors doing in earnest. 



This is a favourite theory, and there is a strong element 

 of truth in it. That it cannot be the whole truth seems 

 to have been shown experimentally. A kitten taken very 

 early from the mother will play profusely without any 

 known possibility of imitative stimulus. 



The second theory of play is Darwinian, and Groos has 

 the credit of having developed it. According to this 

 theory, there are inborn play-instincts, characteristic in 

 form for different types. They may be stimulated by 

 superfluous energy and influenced by imitation, but they 



