XXXVIII. THE CONCEPTS AND THEORIES OF MODERN PHYSICS. By J. B. STALLO. $1.75. XXXIX. THE BRAIN AND ITS FUNCTIONS. By J. LUYS. $1.50. XL. MYTH AND SCIENCE. An Essay. By TITO VIGNOLI. $1.50. XLI. DISEASES OF MEMORY: An Essay in the Positive Psychology. By TH. RIBOT, author of "Heredity." From the French, by WILLIAM HUNTINGTON SMITH. $1.50. XLII. ANTS, BEES, AND WASPS. A Record of Observations on the Habits of the Social Hymenoptera. By Sir JOHN LUBBOCK, Bart., F. R. S., D. C. L., LL. D., etc. $2.00. XLIII. SCIENCE OF POLITICS. By SHELDON AMOS, author of "Science of Law." $1.75. XLIV. ANIMAL INTELLIGENCE. By GEORGE J. ROMANES. $1.75. XLV. MAN BEFORE METALS. By N. JOLY, Correspondent of the Institute. With 148 Illustrations. $1.75. XLVI. THE ORGANS OF SPEECH AND THEIR APPLICATION IN THE FORMATION OF ARTICULATE SOUNDS. By GEORG HERMANN VON MEYER, Professor in Ordinary of Anatomy at the University of Zürich. With 47 Woodcuts. $1.75. New York: D. APPLETON & CO., 1, 3, & 5 Bond Street. THE INTERNATIONAL SCIENTIFIC SERIES. ANIMAL INTELLIGENCE. BY GEORGE J. ROMANES, M. A., LL. D., F. R. S., ZOOLOGICAL SECRETARY OF THE LINNEAN SOCIETY. NEW YORK: D. APPLETON AND COMPANY, 1, 3, AND 5 BOND STREET. 1884. PREFACE. WHEN I first began to collect materials for this work it was my intention to divide the book into two parts. Of these I intended the first to be concerned only with the facts of animal intelligence, while the second was to have treated of these facts in their relation to the theory of Descent. Finding, however, as I proceeded, that the material was too considerable in amount to admit of being comprised within the limits of a single volume, I have made arrangements with the publishers of the 'International Scientific Series' to bring out the second division of the work as a separate treatise, under the title 'Mental Evolution.' This treatise I hope to get ready for press within a year or two.