ON THE ORIGIN OF SPECIES BY MEANS OF NATURAL SELECTION, OR THE PRESERVATION OF FAVOURED RACES IN THE STRUGGLE FOR LIFE. BY CHARLES DARWIN, M.A., F.R.S., &c. FOURTH EDITION, WITH ADDITIONS AND CORRECTIONS. (EIGHTH THOUSAND.) LONDON: JOHN MURRAY, ALBEMARLE STREET. 1866. The right of Translation is reserved. 189. f. 17 BY THE SAME AUTHOR. A NATURALIST'S VOYAGE ROUND THE WORLD; or, A JOURNAL OF RESEARCHES into the NATURAL HISTORY and GEOLOGY of the COUNTRIES visited during the Voyage of H. M. S. Beagle, under the Command of Capt. Frrz-Ror, R. N. Post 8vo. 98. MURRAY. ON THE STRUCTURE AND DISTRIBUTION OF CORAL REEFS. SMITH, ELDER, & Co. GEOLOGICAL OBSERVATIONS ON VOLCANIC ISLANDS. SMITH, ELDER, & Co. GEOLOGICAL OBSERVATIONS ON SOUTH AMERICA. A MONOGRAPH OF THE CIRRIPEDIA. SMITH, ELDER, & Co. With numerous RAY SOCIETY. HARDWICKE. ON THE VARIOUS CONTRIVANCES BY WHICH BRITISH AND FOREIGN ORCHIDS ARE FERTILISED BY INSECTS; and on the GOOD EFFECTS of CROSSING. With Woodcuts. Post 8vo. 9s. MURRAY. ON THE MOVEMENTS and HABITS of CLIMBING PLANTS. Preparing for Publication. DOMESTIC ANIMALS AND CULTIVATED PLANTS; or, The PRINCIPLES of VARIATION, INHERITANCE, REVERSION, CROSSING, INTERBREEDING, and SELECTION, UNDER DOMESTICATION. LONDON: PRINTED BY W. CLOWES AND SONS, STAMFORD STREET, Causes of Variability-Effects of Habit-Correlation of GrowthInheritance-Character of Domestic Varieties-Difficulty of distinguishing between Varieties and Species-Origin of Domestic Varieties from one or more Species-Domestic Pigeons, their Differences and Origin - Principles of Selection anciently followed, their Effects-Methodical and Unconscious Selection-Unknown Origin of our Domestic Productions-Circumstances favourable to Man's power of Selection .. 7-45 CHAPTER II. VARIATION UNDER NATURE. Variability Individual differences - Doubtful species - Wideranging, much-diffused, and common species vary most-Species of the larger genera in each country vary more than the species of the smaller genera-Many of the species of the larger genera resemble varieties in being very closely, but unequally, related to each other, and in having restricted ranges 46-69 CHAPTER III. STRUGGLE FOR EXISTENCE. Its bearing on natural selection - The term used in a wide sense Geometrical ratio of increase Rapid increase of naturalised animals and plants- Nature of the checks to increase - Competition universal-Effects of Climate Protection from the number of individuals - Complex relations of all animals and plants throughout nature-Struggle for life most severe between individuals and varieties of the same species; often severe between species of the same genus-The relation of organism to organism the most important of all relations -- CHAPTER IV. NATURAL SELECTION. Page 70-89 Natural Selection-its power compared with man's selection—its power on characters of trifling importance - its power at all ages and on both sexes· - Sexual Selection - On the generality of intercrosses between individuals of the same species- Circumstances favourable and unfavourable to Natural Selection, namely, intercrossing, isolation, number of individuals - Slow action Extinction caused by Natural Selection - Divergence of Character, related to the diversity of inhabitants of any small area, and to naturalisation - Action of Natural Selection, through Divergence of Character and Extinction, on the descendants from a common parent-Explains the Grouping of all organic beings - Advance in organisation-Low forms preserved · Objections considered Indefinite multiplication of species Summary.. CHAPTER V. LAWS OF VARIATION. 90-156 Effects of external conditions Use and disuse, combined with natural selection; organs of flight and of vision — Acclimatisation-Correlation of growth Compensation and economy of growth-False correlations - Multiple, rudimentary, and lowly organised structures variable-Parts developed in an unusual manner are highly variable: specific characters more variable than generic secondary sexual characters variable-Species of the same genus vary in an analogous manner - Reversions to long-lost characters - Summary . 157-198 CHAPTER VI. DIFFICULTIES ON THEORY. Difficulties on the theory of descent with modification-TransitionsAbsence or rarity of transitional varieties—Transitions in habits of life- Diversified habits in the same species-Species with habits widely different from those of their allies - Organs of extreme perfection - Modes of transition-Cases of difficultyNatura non facit saltum-Organs of small inportance - Organs not in all cases absolutely perfect-The law of Unity of Type and of the Conditions of Existence embraced by the theory of Natural Selection.. Page 199-247 CHAPTER VII. INSTINCT. Instincts comparable with habits, but different in their origin — Instincts graduated — Aphides and ants- Instincts variable— Domestic instincts, their origin — Natural instincts of the cuckoo, ostrich, and parasitic bees - Slave-making ants - Hive-bee, its cell-making instinct - Changes of instinct and structure not necessarily simultaneous - Difficulties on the theory of the Natural Selection of instincts - Neuter or sterile insectsSummary 248-291 CHAPTER VIII. HYBRIDISM. Distinction between the sterility of first crosses and of hybrids Sterility various in degree, not universal, affected by close interbreeding, removed by domestication-Laws governing the sterility of hybrids Sterility not a special endowment, but incidental on other differences, not accumulated by natural selection Causes of the sterility of first crosses and of hybrids-Parallelism between the effects of changed conditions of life and of crossingDimorphism and Trimorphism-Fertility of varieties when crossed and of their mongrel offspring not universal — Hybrids and mongrels compared independently of their fertilitySummary.. 292-338 |