PREFACE. xi 



individual cases. However, I should like to add in this 

 connection that it does not follow, because I have only 

 quoted a small percentage of the letters which I have re- 

 ceived, that all of the remainder have been useless. On 

 the contrary, many of these have served to convey infor- 

 mation and suggestions which, even if not reserved for 

 express quotation in my forthcoming work, have been of 

 use in guiding my judgment on particular points. There- 

 fore I hope that the publication of these remarks may 

 serve to swell the stream of communications into a yet 

 larger flow. ^ 



In all cases where I have occasion to quote statements 

 of fact, which in the present treatise are necessarily 

 numerous, I have made a point of trying to quote 

 verbatim. Only where I have found that the account 

 given by an author or a correspondent might profitably 

 admit of a considerable degree of condensation have I 

 presented it in my own words. 



And here I have to express my very special obligations 

 to Mr. Darwin, who not only assisted me in the most 

 generous manner with his immense stores of information, 

 as well as with his valuable judgment on sundry points 

 of difficulty, but has also been kind enough to place 

 at my disposal all the notes and clippings on animal 

 intelligence which he has been collecting for the last forty 

 years, together with the original MS. of his wonderful 

 chapter on ' Instinct.' This chapter, on being re-cast for 

 the ' Origin of Species,' underwent so merciless an amount 

 of compression that the original draft constitutes a rich 

 store of hitherto unpublished material. In my second 

 work I shall have occasion to draw upon this store more 

 largely than in the present one, and it is needless to add 



' Letters may be addressed to me directly at 18 Cornwall Terrace, 

 Regent's Park, London, JS.W. 



