THE PLAY OF ANIMALS 227 



greater pleasure to be a more effective cause than some one 

 else. We may refer to the races among lambs and kids, 

 wild horses, and asses ; the various forms of " tig " and 

 " follow my leader " in monkeys ; and to other rival 

 exhibitions of agility. Perhaps some forms of dance and 

 song should be included here, when they occur unconnected 

 with courtship. And even when they have some connection 

 with courtship, it is difficult to decide whether the court- 

 ship led to the play, or whether a form of play was utilised 

 in the courtship. 



We may give one instance of the kind of competitive 

 display to which we refer, taking Mr. Hudson's description 

 of the cock-of-the rock (Rupicola) of tropical South America. 

 " A mossy level spot of earth surrounded by bushes is 

 selected for a dancing-place, and kept well cleared of 

 sticks and stones ; round this area the birds assemble, 

 when a cock-bird, with vivid orange-scarlet crest and 

 plumage, steps into it and, with spreading wings and tail, 

 begins a series of movements as if dancing a minuet ; 

 finally, carried away with excitement, he leaps and gyrates 

 in the most astonishing manner, until, becoming exhausted, 

 he retires and another bird takes his place." There are 

 similar displays among uncivilised races of men to-day. 



To sum up : There are many play-instincts among 

 animals ; they have been wrought out in the course of 

 ages, partly as safety-valves for overflowing energy, partly 

 as the muscular correlates of emotion, partly as oppor- 

 tunities for the emergence of variations before too rigorous 

 selection begins, but mainly as periods for educating 

 powers which are essential in after-life. Animals, Groos 

 says, do not simply play because they are young ; they 

 continue young in order that they may play. 



In short, play is so widespread because of its funda- 

 mental importance as the young form of work. The animals 



