VI PREFACE 



following pages, so that I will now quote to the reader 

 a few lines from the writings of others. 



Prof. C. S. Minot, in a review of Prof. C. Lloyd 

 Morgan's " Habit and Instinct/ 5 writes thus : 



"As a naturalist, it has seemed to me that the 

 naturalist's method has an immense future in Psy- 

 chology. The method includes two main factors : 

 the observation of details, and the comparison of 

 homologous phenomena in different forms of life ; and 

 the method starts from the standpoint of evolution. 

 There need be no restriction, of course, upon the three 

 aspects of Psychology which have heretofore prevailed 

 the metaphysical, introspective, and experimental, 

 but there should come soon, and with revolutionary 

 power, not merely enlarged interest in, and sympathy 

 with, Comparative Evolutional Psychology, but more 

 than that eagerness to enter this field of enquiry and 

 to share in harvesting it" (Psych. Rev., vol. iv. No. 3, 

 p. 313). 



Those who do me the honour of reading the pages of 

 this book will learn for themselves how completely 

 I share Professor Minot's views, and that my convic- 

 tions have been followed by corresponding action. 



But one may well ask : Who is able for so great a 

 task ? I know of no higher ideal of the requirements 

 for the worker in Comparative Psychology than that 

 set forth by Prof. Groos in his " Die Spiele der 

 Thiere." He well says : " The author of a psychology 

 of animal play should have, in reality, not alone two, 

 but many souls within his breast." He would have 



