Produced by Bryan Ness, Keith Edkins and the Online Distributed Proofreading Team at https://www.pgdp.net (This file was produced from images generously made available by The Internet Archive/American Libraries.) BIOLOGICAL PUBLICATIONS. THE PRIMARY FACTORS OF ORGANIC EVOLUTION. By _Prof. E. D. Cope_. Cuts, 121. Pp., xvi, 547. Cl., $2.00 (10s.). DARWIN AND AFTER DARWIN. An Exposition of the Darwinian Theory and a Discussion of Post-Darwinian Questions. By _George John Romanes, LL. D., F. R. S., etc._ 1. THE DARWINIAN THEORY. With portrait of Darwin. Pp., 460. Cuts, 125. Second edition. Cloth, $2.00. 2. POST-DARWINIAN QUESTIONS. Heredity and Utility. With portrait of Romanes. Pp., 338. Cloth, $1.50. 3. POST-DARWINIAN QUESTIONS. Isolation and Physiological Selection. With portrait of Mr. J. T. Gulick. Pp., 181. 8vo. Cloth, $1.00. (_The three volumes supplied to one order for $4.00._) A FIRST BOOK IN ORGANIC EVOLUTION. An Introduction to the Study of the Development Theory by _D. Kerfoot_ _Shute, M. D._ Pages, xvi, 285, 39 illustrations--9 in natural colors. Cloth, $2.00 net (7s. 6d. net). AN EXAMINATION OF WEISMANNISM. By _George John_ _Romanes_. Pp., ix, 221. Cloth, $1.00. Paper, 40c. THE PSYCHIC LIFE OF MICRO-ORGANISMS. By _Dr._ _Alfred Binet_. Pp., xii, 120. Cloth, 75c (3s. 6d.). Paper, 30c (1s. 6d.). ON GERMINAL SELECTION. By _August Weismann_. Pp., xii, 61. Paper, 30c (1s. 6d.). ON MEMORY, AND THE SPECIFIC ENERGIES OF THE NERVOUS SYSTEM. By _E. Hering_. Pp., 50. Paper, 20c. A MECHANICO-PHYSIOLOGICAL THEORY OF ORGANIC EVOLUTION. Summary. By _Carl von Naegeli_. Pp., 52. Paper, 20c (9d.). ON ORTHOGENESIS. By _Th. Eimer_. Pp., 56. Paper, 30c. (1s. 6d.). THE PRINCIPLES OF BACTERIOLOGY. By _Dr. Ferdinand_ _Hueppe_. Woodcuts, 28. Pp., 467. $1.75 (7s. 6d.). THE OPEN COURT PUB. CO., CHICAGO. * * * * * ON GERMINAL SELECTION AS A SOURCE OF DEFINITE VARIATION BY AUGUST WEISMANN TRANSLATED FROM THE GERMAN BY THOMAS J. McCORMACK * * * * * SECOND EDITION * * * * * CHICAGO THE OPEN COURT PUBLISHING COMPANY. LONDON AGENTS: KEGAN PAUL, TRENCH, TRUEBNER & CO., LTD. 1902. * * * * * COPYRIGHT BY THE OPEN COURT PUBLISHING CO. 1896 * * * * * {3} PREFACE. The present paper was read in the first general meeting of the International Congress of Zooelogists at Leyden on September 16, 1895. Several points, which for reasons of brevity were omitted when the paper was read, have been re-embodied in the text, and an Appendix has been added where a number of topics receive fuller treatment than could well be accorded to them in a lecture. The address was first printed in _The Monist_ for January, 1896, and afterwards in a German pamphlet.