On the absence of intermediate varieties at the present day - On the nature of extinct intermediate varieties; on their number the lapse of time, as inferred from the rate of denudation and of deposition On the lapse of time as estimated by years. On the poorness of our palæontological collections - On the intermittence of geological formations - On the denudation of granitic areas - On the absence of intermediate varieties in any one formation On the sudden appearance of groups of species-On their sudden appearance in the lowest known fossiliferous strata — Antiquity of the habitable On the slow and successive appearance of new species On their different rates of change Species once lost do not reappear― Groups of species follow the same general rules in their appearance and disappearance as do single species On Extinction. On simultaneous changes in the forms of life throughout the world - Present distribution cannot be accounted for by differences in physical conditions Importance of barriers - Affinity of the productions of the same continent Centres of creation-Means of dispersal, by changes of climate and of the level of the land, and by occasional means -Dispersal during the Glacial period - Alternate Glacial periods in Absence of Batrachians and of terrestrial Mammals - On the relation of the inhabitants of islands to those of the nearest main- land On colonization from the nearest source with subsequent modi- CLASSIFICATION, groups subordinate to groups and difficulties in classification, explained on the theory of descent with modification - Classification of varieties - Descent always used in classification - Analogical or adaptive characters - Affinities, general, complex, and radiating - Extinction separates and defines groups MORPHOLOGY, between members of the same class, between parts of the same individual - - EMBRYOLOGY, laws of, explained by variations not supervening at an early age, and being inherited at a corresponding age RUDIMENTARY ORGANS; their origin explained — RECAPITULATION AND CONCLUSION. Recapitulation of the objections to the theory of Natural Selection — Recapitulation of the general and special circumstances in its favour Causes of the general belief in the immutability of species How far the theory of Natural Selection may be extended Effects of its adoption on the study of Natural History - Con- cluding remarks 404-429 ADDITIONS AND CORRECTIONS TO THE SIXTH EDITION. NUMEROUS small corrections have been made in the last and present editions on various subjects, according as the evidence has become somewhat stronger or weaker. The more important corrections and some additions in the present volume are tabulated on the following page, for the convenience of those interested in the subject, and who possess the fifth edition. The second edition was little more than a reprint of the first. The third edition was largely corrected and added to, and the fourth and fifth still more largely. As copies of the present work will be sent abroad, it may be of use if I specify the state of the foreign editions. The third French and second German editions were from the third English, with some few of the additions given in the fourth edition. A new fourth French edition has been translated by Colonel Moulinié; of which the first half is from the fifth English, and the latter half from the present edition. A third German edition, under the superintendence of Professor Victor Carus, was from the fourth English edition; a fifth is now preparing by the same author from the present volume. The second American edition was from the English second, with a few of the additions given in the third; and a third American edition has been printed from the fifth English edition. The Italian is from the third, the Dutch and three Russian editions from the second English edition, and the Swedish from the fifth English edition. Fifth Sixth Edition. Edition. Chief Additions and Corrections. Page Page 100 68 158 101 220 142 225 145 230 149 231 150 233 151 234 153 248 162 Influence of fortuitous destruction on natural selection. Account of the Ground-Woodpecker of La Plata modified. Transitions through the acceleration or retardation of the The account of the electric organ of fishes added to. Analogical resemblance between the eyes of Cephalopods and Vertebrates. Claparède on the analogical resemblance of the hair-claspers The probable use of the rattle to the Rattle-snake. 214 The statement with respect to young cuckoos ejecting their On the cuckoo-like habits of the Molothrus. The discussion on the fertility of hybrids not having been ac- Extinct forms serving to connect existing groups. Discussion on analogical resemblances, enlarged and modified. On serial homologies, corrected. Mr. E. Ray Lankester on morphology. On the asexual reproduction of Chironomus. On the origin of rudimentary parts, corrected. Natural selection not the exclusive agency in the modi- |