4IO 



NATURE 



[September i, 



genito-urinary system until something more is known 

 about them. 



From this brief sketch it will be gathered that the 

 author has considerably improved the work in most 

 respects ; but we regret to see the terms epi and hypo 

 still used in describing the embryonic layers, instead of 

 the prefixes endo and ecto used by German zoologists, 

 which are greatly preferable, especially in teaching 

 students. We would have liked also to have seen less 

 clarendon type used in the text and restricted to headings 

 only, also the retention of the German system of em- 

 phasising words and passages by means of double spacing 

 between the letters of the type. 



Doubtless the new edition of the " Elements of Com- 

 parative Anatomy of Vertebrates " will continue, and 

 that deservedly, to retain its place amongst students' 

 manuals. J. G. G. 



ANIMAL PLAY. 

 The Play of Animals; a Study of Animal Life and 

 Instinct. By Karl Groos. Translated by Elizabeth 

 J. Baldwin ; with a Preface and Appendix by J. Mark 

 Baldwin. Pp. xxvi -I- 341. (London : Chapman and 

 Hall, Ltd., 1898.) 



THIS interesting little work, the preface to the 

 original German edition of which is dated 1895, 

 presents one very unusual peculiarity. The editor, with 

 the author's approval, has acted the part of the candid 

 friend, and in his preface has given not only a valuable 

 synopsis of the chief contents and object of the book, but 

 has added such careful criticisms on the author's theories 

 as to render further critical observations almost super- 

 fluous, Prof. Baldwin being a well-known authority on 

 subjects akin to those treated by Prof. Groos. 



Not only is the book practically unique in its subject, 

 but it appeals to two distinct classes of readers. In the 

 first, second, and fifth chapters it appeals to the philo- 

 sophical student of animal play as a serious subject ; 

 while the third and fourth chapters are devoted to actual 

 illustrations of this play, and, as charmingly written and 

 authentic anecdotes, will delight a much wider circle. 

 Indeed, to both classes of readers the work may be 

 commended with every confidence. 



The author takes, so to speak, a very serious view of 

 the importance of play in animal development, and treats 

 it with the profundity of research characteristic of the 

 German investigator. He says, for instance (p. 291), 

 that 



"it seems a very mistaken proceeding to characterise 

 play as aimless activity, carried on simply for its own 

 sake. Energetic action may be provocative of pleasure, 

 but it is by no means the only source of the pleasure 

 produced by play." 



And the view that play is a veritable instinct is elabor- 

 ated with great wealth of detail in the second chapter. 

 Here, as the editor remarks, we have full details of such 

 interesting topics as imitation in its relation to play, the 

 inheritance of acquired characters in relation to the rise 

 of instincts, and the plan and function of intelligence in 

 the origin of these primary animal activities. And here, 

 NO. 1505, VOL. 58] 



perhaps, the humanitarian may derive a mitigated satis- 

 faction from the theory (pp. 121 and 122) that the cat's 

 treatment of the captured mouse is not due to the love 

 of torture for torture's sake, but is owing to an instinctive 

 exercise for acquiring skill in the chase, turned later into 

 practical account by the captor. 



The first chapter is an examination of Mr. Herbert 

 Spencer's theory of the " surplus-energy " origin of play, 

 which, if we accept the author's views, must for the future 

 be put aside. Chapter ii., which deals with the biological 

 theory of play, must be read in connection with Chapter 

 v., of which the physiology of play forms the subject ; 

 these three chapters, as already stated, supplying the 

 theoretical and philosophical matter of the book, while 

 the two intermediate chapters afford the detailed facts 

 on which the superstructure rests. 



Some of the author's main theoretical positions are 

 concisely summarised in the following extract from his 

 editor's preface : — 



" He holds play to be an instinct developed by natural 

 selection, . . . and to be on a level 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. ... Its utility is in 

 the main twofold. First, it enables the young animal to 

 exercise himself beforehand in the strenuous and neces- 

 sary functions of its life, and so to be ready for their 

 onset ; and, second, it enables the animal by general 

 instinct to do many things in a playful way, and so to 

 learn for itself much that would otherwise have to be 

 inherited in the form of special instincts ; this puts a 

 premium on intelligence, which thus comes to replace 

 instinct. Either of these utilities. Prof Groos thinks, 

 would ensure and justify the play instinct ; so important 

 are they, that he suggests that the real meaning of 

 infancy is that there may be time for play." 



For the difificulty the editor sees in this conception of 

 play as a pure instinct, the reader must be referred to 

 the work itself, which is long likely to maintain the 

 leading position in a new and important field of inquiry. 



The data on which the author relies as his basis for 

 theorising are necessarily in great part drawn from the 

 writings of others. In the selection of these he appears 

 to have exercised a wise discrimination. His great 

 obligations to Brehm's " Tierleben " are fully acknow- 

 ledged, and we are glad to see that he accepts all the 

 observations of Mr. W. H. Hudson, some of which we 

 believe there has elsewhere been a tendency to discredit. 

 In the main the animals referred to are rightly named, 

 but we shall be surprised if the creatures termed 

 "badgers" on p. 113 of the translation are not really 

 ratels. R. L. 



OUR BOOK SHELF. 

 The Study of Man. By Alfred C. Haddon. Pp. xxxi 



-I- 512. (London : Bliss, Sands, and Co. New York: 



C. P. Putnam's Sons, 1898.) 

 The publication of this volume will doubtless be the 

 means of exciting interest in anthropological inquiries, 

 and adding to the number of scientific students of 

 human-kind. The work is not a systematic treatise on 

 anthropology, but a collection of articles upon various 

 subjects of anthropological study, containing much that 

 is interesting to the serious student, for whose benefit 



