1896. SOME NEW BOOKS. 391 



The Sports of Animals. 



Die Spiele der Thiere. Von Karl Groos, Professor der Philosophie in Giessen. 

 Pp. xvi., 359. Jena: G. Fischer, i8q6. Price 6 marks. 



Professor Groos, in an interesting preface, discusses the relation 

 of his subject to the psychology of man, holding that all sides of the 

 life of the lower creatures may throw light upon man, since among 

 them may be studied the incipient stages of what becomes more 

 highly developed in the higher creature. To the well-known proposi- 

 tion so ably developed by Lewes and Spencer, and shown by Dr. 

 Groos to be due to Schiller, that the frolics of young creatures are an 

 expression of exuberant energy, an overflow of nerve force, he adds 

 the other suggestion that they frequently are a preparation for the 

 important duties of adult Ufe. As a little girl trains herself for a 

 future maternity by devotion to a doll, so the kitten or tiger-cub 

 playmg with a ball may be training itself for its future catching of 

 living prey. 



The first chapter discusses at length the theory of superfluous 

 energy as the cause of play. Admitting to the fullest the physio- 

 logical importance of the principle, the author shows that the root of 

 the matter lies deeper. Animals and men tire themselves out at their 

 games : a dog that has returned from a long walk and is slouching 

 listlessly along with its tongue out of its mouth, if it meets another 

 dog will begin to gambol with it. By instances from many authors 

 he leads up to the conclusion that there is a close connection between 

 instinct and play, and that a deep-seated biological cause must be 

 found for this. 



The second chapter developes this theory of the connection 

 between instinct and play. In a long review of the interpretations 

 placed upon instinct by earlier writers, Dr. Groos gradually makes 

 plain that he adheres most closely to Weismann's conception of 

 instinct as a congenital property built up chiefly by selection and 

 owing little, if anything, to inheritance of acquired characters. In 

 the case of higher animals instinct becomes more and more merged 

 in intelligent action. He believes, not that these higher animals play 

 because they have youth as a time of overflowing energy, but that 

 they have youth in order that they may play. Their instincts operate 

 before they are needed for the real business of life, and the continual 

 exercise of them in play changes the cast-iron congenital instinct into 

 a more flexible habit, readier of adaptation by the intelligence to the 

 varying exigencies of real life. 



In the third and longest chapter of the volume Professor Groos 

 has brought together in a systematic fashion an enormous collection 

 of the facts regarding the play of animals. He classifies plays as 

 follows : — (i) Experimental, in which the very young of all the higher 

 animals, as soon as they arrive at the independent use of their facul- 

 ties, or limbs and jaws, restlessly examine and experiment with every 

 object that comes within their reach. Among these experiments, for 

 instance, he puts the case of Miss Romanes' young monkey which 

 took the greatest pleasure in learning to unscrew and rescrew the 

 handle of a brush. (2) Locomotion, in which young animals practise 

 their future modes of movement. Such are seen in the racing and 

 chasing of young dogs, in the vertical jumping of young mountain- 

 dwellers like chamois and goats, or in the distance jumping of young 

 buck. (3) In the hunting games of the young, the instincts tending 

 towards future use, are more clearly in evidence. Young lions, tigers, 

 and cats play with inanimate objects like balls or stones, pushing 



