have not, at least, been published to the author's knowledge; and for these he alone is responsible. To some, the chapters on the mode of evolution of the higher forms will appear too hypothetical; but they are presented only as hypotheses, and the reader will be enabled to judge how far the facts referred to in corroboration of the views expressed justify them. The author has endeavoured to give the theory of evolution from the point of view of a physiologist as well as of a naturalist. He has attempted (it is to be feared insufficiently) to acknowledge his obligations in a list of works referred to as well as in footnotes, but would not omit on the present occasion to thank those numerous friends who have for years aided him in the prosecution of his favourite studies. Acknowledgments are especially due to Sir James Paget, Mr. Savory, Dr. Hooker, and Professor Flower, for their past teaching and ever ready advice. Colville Gardens, W. May 12, 1873. WORKS QUOTED OR REFERRED TO. AGASSIZ, A. Bulletin of the Museum of Comparative Zoology. AGASSIZ, L. Essay on Classification. BAIN. Senses and Intellect, 1855. BEAUMONT, E. de. Notice sur les Systèmes de Montagnes. BENEDEN, E. VAN. Recherches sur le Signification de l'Euf. BESSEL. Köll. Zeits. für wissenschaft. Zool. CARPENTER, W. B. Physiology, 7th edit. COPE. "Origin of Genera," Proc. Ac. Nat. Sci. Phil. 1868. DARWIN, CHARLES. Origin of Species, 6th edit. De Candolle, A. Géographie Botanique, 1855. GANNIN. Köll. Zeits. für wissenschaft. Zool. HÄCKEL, E. Morphologie generelle. HOOKER, J. D. Flora of New Zealand. Address to British Association at Norwich. HUXLEY. Vertebrated Animals, 1871. Man's Place in Nature. LOWNE, B. T. Anatomy of the Fly. LUBBOCK, Sir J. Origin of Civilization. Principles of Geology, 10th edit. LYELL, Sir C. MALEBRANCHE. Ninth Conversation on Metaphysics. vili WORKS QUOTED OR REFERRED TO. MAX MÜLLER. The Science of Language. MILL. Logic, 5th edit. PAGET, Sir J. Surgical Pathology. PARKER, W. K. "The Fowl's Skull," Phil. Trans. "Development of the Frog's Skull," Phil. Trans. RICHARDSON, B. W. Medical Times, Feb. 18, 1871. SIMON, J. Natural Religion, translated by Cole. Lond. 1857. SPENCER, H. First Principles of Philosophy, 2nd edit. Principles of Biology. THOMSON, WYVILLE. Depths of the Sea. TYNDALL. Heat a mode of Motion, 3rd edit. WEISSMANN. Köll. Zeitschrift für wissenschaftliche Zoologie. WHEWELL. Philosophy of Discovery. Philosophy of the Inductive Sciences. Chapter CONTENTS. Page |