APPENDIX I. 



NOTICES OF BOOKS. 



Die Spiele der Thiere. By Karl Groos. Jena: G. Fischer, 1896. Pp. xvi. , 359. 



The chief point which is worked out in this book is that animal play depends on a 

 deeply planted instinct of the greatest importance in the struggle for existence. Spencer's view 

 that play is the expression of overflow of energy is held to be only a small part of the truth. 

 Play is regarded as the instinctive performance, without real cause, of actions resembling those 

 useful in the actual struggle for life. Superfluous energy is the most favourable condition for 

 play, but the author points out that the impulse to play is so strong that animals will react to a 

 stimulus to play even when in an exhausted condition. 



The second chapter contains a good account of the views which have been held on the 

 subject of instinct, the author's own position being very close to that of Weismann. Play being 

 regarded as an instinct, the play of young animals is naturally most fully considered. The im- 

 portance of play is rated so highly that the author supposes that "youth owes its existence to 

 the necessity for play". In the next two chapters, in which the games of animals are con- 

 sidered in detail, the author's views are illustrated by copious examples drawn from very wide 

 sources, but chiefly from the accounts of those who have observed animals in a state of nature. 

 One of the most quoted authors in this respect is Hudson. The simplest kind of play is called 

 "experimenting," and this term is employed for the actions of young animals, by means of 

 which they obtain command over their own movements and over external objects. Under the 

 heading of play of movement are included most of the examples quoted by Spencer in support 

 of his theory. Hunting and fighting games are fully considered, and they give strong support 

 to the author's view. In considering such play as that of a cat with a caught mouse, strong 

 objection is made to Romanes' view that animals delight in torture for torture's sake ; such 

 play is rather regarded as instinctive activity adapted to improve skill. Instances are given in 

 which building and nursing appear to have occurred in play. Imitation games are considered, 

 and imitation is regarded as an instinct closely associated with the play instinct. 



The performances of courtships are considered separately, differing from other kinds of 

 play in that they have a real occasion. The subject of sexual selection is fully discussed. The 

 author is sceptical on the question of conscious choice by the female, and he thinks that there 

 is distinct evidence that pairing takes place before the courtship performances begin. He re- 

 gards it as necessary for the preservation of the species that there should be some restraint of 

 the sexual act, and he supposes that this restraint is provided by instinctive coyness of the 

 female, and that the performances are carried out in order to overcome this coyness by pro. 

 ducing sexual excitement ; coquetry is the result of the struggle of two opposed instincts. A 

 full account is given of the various forms which these performances may take, and instances 

 are given in which they have been observed in young animals. 



In the final chapter the psychology of play is considered. The games of young animals 

 are held to be purely instinctive, and their only mental accompaniment to be the pleasure 

 attending the satisfaction of an instinct. In the adult animal it is believed that play is often 

 accompanied by consciousness of the unreal nature of the activity, the chief element in this 

 consciousness being the pleasure of power. Instances of dissimulation in animals are quoted 

 in support of the existence of consciousness of sham-occupation. In conclusion, the relation of 

 animal play to the various forms of art is dealt with, and this part of the subject will no doubt 

 be more fully treated in another work on human play which is promised by the author. 



Text-book of the Embryology of Invertebrates. By E. Korschelt and K. Heider. Translation 

 into English by E. L. Mark and W. Mc. M. Woodworth, with additions by the Authors 

 and Translators. Part I. London : Swan Sonnenschein & Co. , Limited. New York : 

 Macmillan & Co. , 1895. 



This volume of 466 pp. , with 225 illustrations, has been eagerly awaited. The original 

 is too familiar to those who read German to need comment here ; suffice it to say that it deals 

 in a lucid manner with the development of the Invertebrata, including the Enteropneusta and 

 Rotatoria, with the exception of the Mollusca, Brachiostoma, and Arthropoda. Prof. Mark's 



B 



