I have found to be of great use in guiding my selection of instances, for where statements of fact which present nothing intrinsically improbable are found to be unconsciously confirmed by different observers, they have as good a right to be deemed trustworthy as statements which stand on the single authority of a known observer, and I have found the former to be at least as abundant as the latter. Moreover, by getting into the habit of always seeking for corroborative cases, I have frequently been able to substantiate the assertions of known observers by those of other observers as well or better known.

So much, then, for the principles by which I have been guided in the selection of facts. As to the arrangement of the facts, I have taken the animal kingdom in ascending order, and endeavoured to give as full a sketch as the selected evidence at my disposal permitted of the psychology which is distinctive of each class, or order, and, in some cases, family, genus, or even species. The reason of my entering into greater detail with some natural groups than with others scarcely requires explanation. For it is almost needless to say that if the animal kingdom were classified with reference to Psychology instead of with reference to Anatomy, we should have a very different kind of zoological tree from that which is now given in our diagrams. There is, indeed, a general and, philosophically considered, most important parallelism running through the whole animal kingdom between structural affinity and mental development; but this parallelism is exceedingly rough, and to be traced only in broad outlines, so that although it is convenient for the purpose of definite arrangement to take the animal kingdom in the order presented by zoological classification, it would be absurd to restrict an inquiry into Animal Psychology by any considerations of the apparently disproportionate length and minute subdivision with which it is necessary to treat some of the groups. Anatomically, an ant or a bee does not require more consideration than a beetle or a fly; but psychologically there is need for as great a difference of treatment as there is in the not very dissimilar case of a monkey and a man.

Throughout the work my aim has been to arrive at definite principles rather than to chronicle mere incidents—an aim which will become more apparent when the work as a whole shall have been completed. Therefore it is that in the present volume I have endeavoured, as far as the nature and circumstances of the inquiry would permit, to suppress anecdote. Nevertheless, although I have nowhere introduced anecdotes for their own sake, I have found it unavoidable not to devote much the largest part of the present essay to their narration. Hence, with the double purpose of limiting the introduction of anecdotes as much as possible, and of not repeating more than I could help anecdotes already published, I have in all cases, where I could do so without detriment to my main object, given the preference to facts which have been communicated to me by friends and correspondents. And here I may fitly take the opportunity of expressing my thanks and obligations to the latter, who in astonishing numbers have poured in their communications during several years from all quarters of the globe. I make this statement because I desire to explain to all my correspondents who may read this book, that I am not the less sensible of their kindness because its bounty has rendered it impossible for me to send acknowledgments in 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 received, that all of the remainder have been useless. On the contrary, many of these have served to convey information 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. Therefore I hope that the publication of these remarks may serve to swell the stream of communications into a yet larger flow.[1]

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 that in all cases where I do draw upon it I shall be careful to state the source to which I am indebted.

[The above was written when I sent this work to the publishers several months ago, and I have thought it best to leave the concluding paragraph as it originally stood. But in making this explanation, I cannot allude to the calamity which has since occurred without paying my tribute, not alone to the memory of the greatest genius of our age, but still more, and much more, to the memory of a friend so inexpressibly noble, kind, and generous, that even my immense admiration of the naturalist was surpassed by my loving veneration for the man.]

CONTENTS.