PRE FACE. 



It will be observed that the title of this volume is " Mental 

 Evolution in Animals." The reasons which have led me to 

 depart from my intention (as expressed in the Preface of 

 "Animal Intelligence") to devote the present essay to mental 

 evolution in man as well as in animals, are given in the 

 introductory chapter. 



It may appear that in the following pages a somewhat 

 disproportionate amount of space has been allotted to the 

 treatment of Instinct ; but, looking to the confusion which 

 prevails with reference to this important branch of psychology 

 in the writings of our leading authorities, I have deemed it 

 desirable to consider the subject exhaustively. 



It is, I think, desirable briefly to explain the circum- 

 stances under which I have been enabled to produce so much 

 hitherto unpublished material from the MSS of the late 

 Mr. Darwin, and also to state the extent to which I have 

 availed myself of such of this unpublished material as came 

 into my hands. As I have already explained, in the Preface 

 of " Animal Intelligence," Mr. Darwin himself gave me all his 

 MSS relating to psychological subjects, with the request that 

 I should publish any parts of them that I chose in my works 

 on Mental Evolution. But after his death I felt that the cir- 

 cumstances with reference to this kind offer were changed, 

 and that I should scarcely be justified in appropriating so 

 much material, the value of which had become enhanced. I 

 therefore published at the Linnean Society, and with the 

 consent of Mr. Darwin's family, as much of this material as 



