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| Introduction to the Dover Edition | |
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| Introduction | |
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| Variation under Domestication | |
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| Causes of Variability | |
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| Effects of Habit | |
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| Correlation of Growth | |
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| Inheritance | |
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| Character of Domestic Varieties | |
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| Difficulty of distinguishing between Varieties and Species | |
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| Origin of Domestic Varieties from one or more Species | |
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| Domestic Pigeons, their Differences and Origin | |
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| Principle of Selection anciently followed, its Effects | |
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| Methodical and Unconscious Selection | |
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| Unknown Origin of our Domestic Productions | |
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| Circumstances favourable to Man's power of Selection | |
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| Variation under Nature | |
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| Variability | |
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| Individual Differences | |
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| Doubtful species | |
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| Wide ranging, much diffused, and common species vary most | |
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| Species of the larger genera in any country vary more than the species of the smaller genera | |
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| 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 | |
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| Struggle for Existence | |
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| Bears on natural selection | |
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| The term used in a wide sense | |
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| Geometrical powers of increase | |
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| Rapid increase of naturalised animals and plants | |
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| Nature of the checks to increase | |
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| Competition universal | |
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| Effects of climate | |
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| Protection from the number of individuals | |
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| Complex relations of all animals and plants throughout nature | |
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| Struggle for life most severe between individuals and varieties of the same species; often severe between species of the same genus | |
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| The relation of organism to organism the most important of all relations | |
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| Natural Selection | |
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| Natural Selection | |
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| Its power compared with man's selection | |
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| Its power on characters of trifling importance | |
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| Its power at all ages and on both sexes | |
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| Sexual Selection | |
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| On the generality of intercrosses between individuals of the same species | |
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| Circumstances favourable and unfavourable to Natural Selection, namely, intercrossing, isolation, number of individuals | |
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| Slow action | |
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| Extinction caused by Natural Selection | |
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| Divergence of Character, related to the diversity of inhabitants of any small area, and to naturalisation | |
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| Action of Natural Selection, through Divergence of Character and Extinction, on the descendants from a common parent | |
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| Explains the Grouping of all organic beings | |
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| Laws of Variation | |
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| Effects of external conditions | |
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| Use and disuse, combined with natural selection; organs of flight and of vision | |
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| Acclimatisation | |
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| Correlation of growth | |
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| Compensation and economy of growth | |
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| False correlations | |
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| Multiple, rudimentary, and lowly organised structures variable | |
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| Parts developed in an unusual manner are highly variable: specific characters more variable than generic: secondary sexual characters variable | |
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| Species of the same genus vary in an analogous manner | |
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| Reversions to long-lost characters | |
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| Summary | |
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| Difficulties on Theory | |
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| Difficulties on the theory of descent with modification | |
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| Transitions | |
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| Absence or rarity of transitional varieties | |
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| Transitions in habits of life | |
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| Diversified habits in the same species | |
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| Species with habits widely different from those of their allies | |
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| Organs of extreme perfection | |
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| Means of transition | |
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| Cases of difficulty | |
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| Natura non facit saltum | |
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| Organs of small importance | |
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| Organs not in all cases absolutely perfect | |
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| The law of Unity of Type and of the Conditions of Existence embraced by the theory of Natural Selection | |
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| Instinct | |
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| Instincts comparable with habits, but different in their origin | |
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| Instincts graduated | |
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| Aphides and ants | |
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| Instincts variable | |
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| Domestic instincts, their origin | |
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| Natural instincts of the cuckoo, ostrich, and parasitic bees | |
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| Slave-making ants | |
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| Hive-bee, its cell-making instinct | |
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| Difficulties on the theory of the Natural Selection of instincts | |
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| Neuter or sterile insects | |
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| Summary | |
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| Hybridism | |
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| Distinction between the sterility of first crosses and of hybrids | |
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| Sterility various in degree, not universal, affected by close interbreeding, removed by domestication | |
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| Laws governing the sterility of hybrids | |
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| Sterility not a special endowment, but incidental on other differences | |
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| Causes of the sterility of first crosses and of hybrids | |
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| Parallelism between the effects of changed conditions of life and crossing | |
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| Fertility of varieties when crossed and of their mongrel offspring not universal | |
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| Hybrids and mongrels compared independently of their fertility | |
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| Summary | |
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| On the Imperfection of the Geological Record | |
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| On the absence of intermediate varieties at the present day | |
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| On the nature of extinct intermediate varieties; on their number | |
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| On the vast lapse of time, as inferred from the rate of deposition and of denudation | |
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| On the poorness of our palaeontological collections | |
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| On the intermittence of geological formations | |
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| On the absence of intermediate varieties in any one formation | |
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| On the sudden appearance of groups of species | |
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| On their sudden appearance in the lowest known fossiliferous strata | |
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| On the Geological Succession of Organic Beings | |
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| On the slow and successive appearance of new species | |
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| On their different rates of change | |
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| Species once lost do not reappear | |
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| Groups of species follow the same general rules in their appearance and disappearance as do single species | |
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| On Extinction | |
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| On simultaneous changes in the forms of life throughout the world | |
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| On the affinities of extinct species to each other and to living species | |
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| On the state of development of ancient forms | |
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| On the succession of the same types within the same areas | |
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| Summary of preceding and present chapters | |
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| Geographical Distribution | |
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| Present distribution cannot be accounted for by differences in physical conditions | |
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| Importance of barriers | |
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| Affinity of the productions of the same continent | |
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| Centres of creation | |
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| Means of dispersal, by changes of climate and of the level of the land, and by occasional means | |
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| Dispersal during the Glacial period co-extensive with the world | |
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| Geographical Distribution-continued | |
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| Distribution of fresh-water productions | |
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| On the inhabitants of oceanic islands | |
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| Absence of Batrachians and of terrestrial Mammals | |
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| On the relation of the inhabitants of islands to those of the nearest mainland | |
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| On colonisation from the nearest source with subsequent modification | |
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| Summary of the last and present chapters | |
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| Mutual Affinities of Organic Beings: Morphology: Embryology: Rudimentary Organs | |
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| Classification, groups subordinate to groups | |
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| Natural system | |
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| Rules and difficulties in classification, explained on the theory of descent with modification | |
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| Classification of varieties | |
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| Descent always used in classification | |
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| Analogical or adaptive characters | |
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| Affinities, general, complex and radiating | |
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| Extinction separates and defines groups | |
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| Morphology, between members of the same class, between parts of the same individual | |
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| Embryology, laws of, explained by variations not supervening at an early age, and being inherited at a corresponding age | |
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| Rudimentary Organs; their origin explained | |
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| Summary | |
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| Recapitulation and Conclusion | |
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| Recapitulation of the difficulties on the theory of Natural Selection | |
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| Recapitulation of the general and special circumstances in its favour | |
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| Causes of the general belief in the immutability of species | |
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| How far the theory of natural selection may be extended | |
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| Effects of its adoption on the study of Natural history | |
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| Concluding remarks | |
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| Index | |