24 THE PLAY OF ANIMALS. 



not be sufficiently developed and trained for all these 

 tasks. Moreover, much would be wanting in the struc- 

 ture of his skeleton, much that must be supplied by func- 

 tional adaptation during the life of each individual, even 

 in the period of growth. The thought presents itself 

 here that it must be the iron hand of natural selection 

 that brings into bold relief without too compelling in- 

 sistence and apparently without serious motive — namely, 

 by means of play — what will later be so necessary. There 

 need not be any particular superfluity of energy; so long 

 as only a small remnant of unemployed force is present 

 the animal will follow the law that heredity has stamped 

 upon him. 



Thus we see that the explanation of play by means 

 of the overflow-of -energy theory proves to be unsatisfac- 

 tory. A condition of superabundant nervous force is 

 always, I must again emphatically reiterate, a favourable 

 one for play, but it is not its motive cause, nor, as I 

 believe, a necessary condition of its existence. Instinct 

 alone is the real foundation of it. Foundation, I say, 

 because all play is not purely instinctive activity. On 

 the contrary, the higher we ascend in the scale of exist- 

 ence the richer and finer become the psychological phe- 

 nomena that supplement the mere natural impulse, en- 

 nobling it, elevating it, and tending to conceal it under 

 added details. 



But the fundamental idea from which we must pro- 

 ceed is instinct. My first task must be the examination 

 of instinct; and after a longer, but I hope not altogether 

 uninteresting, exposition, I shall return to the points 

 made above and give them more adequate treatment. 



