274 POPULAR SCIENCE MONTHLY. 



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SPECIAL BOOKS. 



In The Play of Animals* we are offered a book upon an essentially new 

 topic ; for, although much has been written concerning the habits and 

 intelligence of animals, no special consideration has been given to their 

 play or its psychic significance. The survey of this virgin territory seems 

 to the critical reader to have disclosed such limitless area to Professor 

 G-roos that he fails to indicate its legitimate boundaries. He confesses 

 himself overcome by a sense of its vastness, stating that the " versatility 

 needed for a thorough investigation is so comprehensive that it is unattain- 

 able by an ordinary mortal." 



Play, he finds, is not " an aimless activity carried on for its own sake" ; 

 neither is it the product of surplus physical energy, as Mr. Spencer defines 

 it, for in youth there is playfulness without this condition. Instincts use- 

 ful in preserving the species appear before they are seriously needed, and 

 are utilized in play, which serves as preparation for the tasks of life. 

 " Animals do not play because they are young, but have a period of youth 

 in order to play." 



The special ends accomplished by play are control of the body, com- 

 mand of the means of locomotion, agility in pursuit of prey and in escap- 

 ing danger, and prowess in fighting. The games pursued in attaining these 

 ends are classified in nine groups, beginning with those of experimentation 

 and ending with those referred to curiosity. They include plays of move- 

 ment, hunting, fighting, love, construction, nursing, and imitation. For all 

 of these Professor Groos finds but one instinct of play responsible, supple- 

 mented by the instinct of imitation. He enters into an elaborate discussion 

 of instinct, giving an outline of Weismann's theory of heredity and the views 

 of various writers. He adopts Herbert Spencer's definition of instinct as a 

 complex reflex act, referring its origin to the operation of natural selection, 

 acknowledging the process to be beyond our grasp. In seeking to explain 

 bird song and the love play of animals, the theory of sexual selection is 

 not accepted by him without qualification ; a modification of the Darwinian 

 principle is suggested in which the female exerts an unconscious choice. 

 The psychic characteristics of play are the pleasure following satisfaction 

 of instinct, energetic action and joy in the acquirement of power. Tbe 

 animal at first masters its own bodily movements, then seeks the conquest 

 of other animals and inanimate objects. When a certain facility in play 

 has been gained a higher intellectual stage is entered upon, that of make- 

 believe, or playing a part. This state of conscious self-illusion is reached 

 by many of the higher animals. Psychically, it indicates a divided con- 

 sciousness, and occupies a place between the ordinary state and the ab- 

 normal ones of hypnosis and hysteria. To this condition Professor Groos 

 ascribes the genesis of artistic production, an hypothesis that he has elabo- 

 rated more fully in Einleitung in die Aesthetik. 



The experimental plays of animals, divided into those of courtship, imi- 

 tation, and construction, correspond to the principles of self exhibition, 



* The Play of Animals. By Karl Grooa. Translated by Elizabeth L. Baldwin. New York : 

 D. Appleton and Company. Pp. 341. Price, $1.75. 



