THE DEVELOPMENT OF ORGANISMS 8ii 



observers have described among ants. There is energetic wrestling 

 and the hke, but no discharge of poison or actual wounding. 



Perhaps one may recognise another type which may be called 

 playful experiment, when animals test things, often pulling them 

 to pieces; or test themselves, often performing interesting but 

 useless feats; or test their neighbours, discovering how they will 

 respond to sundry provocations. The difficulty is to distinguish these 

 playful experiments from the ways in which many well-endowed 

 young animals feel their way about in their environment. But 

 Hamerton describes how his young goats would spend hours in 

 jumping in and out of a basket, or would try to upset the artist by 

 getting under his seat, or would tease the big dog to the limit of his 

 endurance. Miss Romanes gave a circumstantial account of the 

 experiments of her Capuchin monkey. "He is very fond of upsetting 

 things, but he always takes great care that they do not fall upon 

 himself. Thus he will pull a chair towards him till it is almost over- 

 balanced; then he intently fixes his eyes on the top bar of the back, 

 and, as he sees it coming over his way, darts from imdemeath, and 

 watches the fall with great delight; and similarly with heavier 

 things. There is a washhand-stand, for example, which he has upset 

 several times, and always without hurting himself." For such 

 behaviour as this it is difficult to use any other word but play, or 

 to refuse to call it experimental. 



Along this line the subtlest forms of play are found in apes, where 

 experimenting may go far, and sometimes become sheer mischief. 

 Thus we have watched an impish Indian monkey pulling tiles off 

 an old woman's roof, and returning time after time, until one had 

 to give up stoning him away, and leave the old lady to her fate. 

 A chimpanzee often shows what looks like delight in being a tease, 

 and an entirely useless activity may be repeated over and over 

 again. The play may become a ploy. Thus a chimpanzee wiU entice 

 a hen with bread and pull the reward away at the last minute, 

 repeating the trick many times with evident gusto. Or it will attract 

 a hen close to the cage and then give her a sudden poke with a stick 

 when she is preoccupied with her food. Do not such monkey-tricks 

 seem well up to the level of the practical joke, and sometimes even 

 to "ragging" .? 



Of interest are those cases where playing — or something much 

 like playing — is continued long after youth is past. This is familiar 

 in the case of domestic dogs; but it is also exhibited in natural 

 conditions, for instance by the otter. This extension of play may be 

 sometimes associated with the mother's habit of playing with succes- 

 sive litters of young ones year after year. But this interpretation 

 does not apply to all cases, for instance to the communal playing of 

 full-grown penguins on the sea-ice. Thus Dr. Murray Levick has 

 described the diving ploys in which the succession may be so rapid 



