Recent Biology 379 



treated. Together they furnish the philosophical and theoreti- 

 cal basis of the book, as the chapters in between furnish the 

 detailed data of fact. I shall return to the biological matter 

 below. Chapters III. and IV. go into the actual ' Plays of 

 Animals ' with a wealth of detail, richness of literary information, 

 and soundness of critical interpretation which are most heartily 

 to be commended. Indeed, the fact that a pioneer book on this 

 subject is, at the same time, one of such unusual value, both 

 as science and as theory, should be a matter of congratulation 

 to workers in biology and in psychology. The collected cases, 

 the classification of animal plays, as well as the setting of 

 interpretation in which Professor Groos has placed them all 

 are likely to remain, I think, as a piece of work of excellent 

 quality in a new but most important field of inquiry. 



As to the plays which animals indulge in, Professor Groos 

 classifies them as follows : ' Experimenting,' ' Plays of Move- 

 ment,' ' Play-Hunting ' (' with real living booty,' ' with play 

 living booty,' ' with inanimate play booty '), ' Play-fighting ' 

 ('teasing, scuffling among young animals,' 'play-fighting among 

 adult animals'), so-called 'Building Art,' 'Nursing' plays, 

 ' Imitation ' plays, ' Curiosity,' ' Pairing ' plays, ' Courting by 

 Means of Play of Movements,' ' Courting by the Exhibition of 

 Colours and Forms,' ' Courting by Noises and Tones,' ' Coquetry 

 on the Part of the Female.' 



With this general and inadequate notice of the divisions and 

 scope of the book, I may throw together in a few sentences the 

 main theoretical positions to which the author's study brings 

 him. He holds play to be an instinct 1 developed by natural 

 selection (for he does not accept the inheritance of acquired 

 characters), and to be on a level exactly with the other instincts 

 which are developed for their utility. It is very near, in 

 its origin and function, to the instinct of imitation, but yet 

 they are distinct (a word more below on the relation between 

 play and imitation). Its utility is, in the main, twofold : first, 



1 Modified in The Play of Man in a way which makes the word 'impulse' 

 a better designation, in the author's maturer view. This substitution of 

 terms may be made throughout this review. 



