Most works on mind in the lower animals are large and ponderous volumes, replete with technicalities, and unfit for the general reader; therefore the author of this book has endeavored to present the evidences of mental action, in creatures lower than man, in a clear, simple, and brief form. He has avoided all technicalities, and has used the utmost brevity consistent with clearness and accuracy. He also believes that metaphysics has no place in a discussion of psychology, and has carefully refrained from using this once powerful weapon of psychologists.

            Many of the data used by the authors of more pretentious works are second-hand or hearsay; the author of this treatise, however, has no confidence in the accuracy of such material, therefore he has not made use of any such data. His material has been thoroughly sifted, and the reader may depend upon the absolute truth of the evidence here presented.

            The author does not claim infallibility; some of his conclusions may be erroneous; he believes, however, that future investigation will prove the verity of every proposition that is advanced in this book. These propositions have been formulated only after a twenty-years study of biology in all of its phases.