My second, and much more important object, is that of considering the facts of animal intelligence in their relation to the theory of Descent. With the exception of Mr. Darwin's admirable chapters on the mental powers and moral sense, and Mr. Spencer's great work on the Principles of Psychology, there has hitherto been no earnest attempt at tracing the principles which have been probably concerned in the genesis of Mind. Yet there is not a doubt that, for the present generation at all events, no subject of scientific inquiry can present a higher degree of interest; and therefore it is mainly with the view of furthering this inquiry that I have undertaken this work. It will thus be apparent that the present volume, while complete in itself as a statement of the facts of Comparative Psychology, has for its more ultimate purpose the laying of a firm foundation for my future treatise on Mental Evolution. But although, from what I have just said, it will be apparent that the present treatise is preliminary to a more important one, I desire to emphasise this statement, lest the critics, in being now presented only with a groundwork on which the picture is eventually to be painted, should deem that the art displayed is of somewhat too commonplace a kind. If the present work is read without reference to its ultimate object of supplying facts for the subsequent deduction of principles, it may well seem but a small improvement upon the works of the anecdote-mongers. But if it is remembered that my object in these pages is the mapping out of animal psychology for the purposes of a subsequent synthesis, I may fairly claim to receive credit for a sound scientific intention, even where the only methods at my disposal may incidentally seem to minister to a mere love of anecdote.