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On the Origin of Species by Means of Natural Selection,
or the
Preservation of Favoured Races in the Struggle for Life.
By Charles Darwin
Contents
Introduction
Chapter I(A,B, C)
Variation under Domestication
Causes of Variability -- Effects of Habit -- Correlation of Growth --Inheritance -- Character of Domestic Varieties -- Difficulty ofdistinguishing between Varieties and Species -- Origin of DomesticVarieties from one or more Species -- Domestic Pigeons, their Differencesand Origin -- Principle of Selection anciently followed, its Effects --Methodical and Unconscious Selection -- Unknown Origin of our DomesticProductions -- Circumstances favourable to Man's power of Selection.
Chapter II
Variation under Nature
Variability -- Individual Differences -- Doubtful species -- Wide ranging,much diffused, and common species vary most -- Species of the larger generain any country vary more than the species of the smaller genera -- Many ofthe species of the larger genera resemble varieties in being very closely,but unequally, related to each other, and in having restricted ranges.
Chapter III(A,B)
Struggle for Existence
Bears on natural selection -- The term used in a wide sense -- Geometricalpowers of increase -- Rapid increase of naturalised animals and plants --Nature of the checks to increase -- Competition universal -- Effects ofclimate -- Protection from the number of individuals -- Complex relationsof all animals and plants throughout nature -- Struggle for life mostsevere between individuals and varieties of the same species; often severebetween species of the same genus -- The relation of organism to organismthe most important of all relations.
Chapter IV(A,B, C)
Natural Selection
Natural Selection -- its power compared with man's selection -- its poweron characters of trifling importance -- its power at all ages and on bothsexes -- Sexual Selection -- On the generality of intercrosses betweenindividuals of the same species -- Circumstances favourable andunfavourable to Natural Selection, namely, intercrossing, isolation, numberof individuals -- Slow action -- Extinction caused by Natural Selection --Divergence of Character, related to the diversity of inhabitants of anysmall area, and to naturalisation -- Action of Natural Selection, throughDivergence of Character and Extinction, on the descendants from a commonparent -- Explains the Grouping of all organic beings.
Chapter V(A,B, C)
Laws of Variation
Effects of external conditions -- Use and disuse, combined with naturalselection; organs of flight and of vision -- Acclimatisation -- Correlationof growth -- Compensation and economy of growth -- False correlations --Multiple, rudimentary, and lowly organised structures variable -- Partsdeveloped in an unusual manner are highly variable: specific charactersmore variable than generic: secondary sexual characters variable --Species of the same genus vary in an analogous manner -- Reversions tolong-lost characters -- Summary.
Chapter VI(A,B, C)
Difficulties on Theory
Difficulties on the theory of descent with modification -- Transitions --Absence or rarity of transitional varieties -- Transitions in habits oflife -- Diversified habits in the same species -- Species with habitswidely different from those of their allies -- Organs of extreme perfection-- Means of transition -- Cases of difficulty -- Natura non facit saltum --Organs of small importance -- Organs not in all cases absolutely perfect --The law of Unity of Type and of the Conditions of Existence embraced by thetheory of Natural Selection.
Chapter VII(A,B, C)
Instinct
Instincts comparable with habits, but different in their origin --Instincts graduated -- Aphides and ants -- Instincts variable -- Domesticinstincts, their origin -- Natural instincts of the cuckoo, ostrich, andparasitic bees -- Slave-making ants -- Hive-bee, its cell-making instinct -- Difficulties on the theory of the Natural Selection of instincts --Neuter or sterile insects -- Summary.
Chapter VIII(A,B)
Hybridism
Distinction between the sterility of first crosses and of hybrids --Sterility various in degree, not universal, affected by closeinterbreeding, removed by domestication -- Laws governing the sterility ofhybrids -- Sterility not a special endowment, but incidental on otherdifferences -- Causes of the sterility of first crosses and of hybrids --Parallelism between the effects of changed conditions of life and crossing-- Fertility of varieties when crossed and of their mongrel offspring notuniversal -- Hybrids and mongrels compared independently of their fertility-- Summary.
Chapter IX(A,B)
On the Imperfection of the Geological Record
On the absence of intermediate varieties at the present day -- On thenature of extinct intermediate varieties; on their number -- On the vastlapse of time, as inferred from the rate of deposition and of denudation --On the poorness of our palaeontological collections -- On the intermittenceof geological formations -- On the absence of intermediate varieties in anyone formation -- On the sudden appearance of groups of species -- On theirsudden appearance in the lowest known fossiliferous strata.
Chapter X(A,B, C)
On the Geological Succession of Organic Beings
On the slow and successive appearance of new species -- On their differentrates of change -- Species once lost do not reappear -- Groups of speciesfollow the same general rules in their appearance and disappearance as dosingle species -- On Extinction -- On simultaneous changes in the forms oflife throughout the world -- On the affinities of extinct species to eachother and to living species -- On the state of development of ancient forms-- On the succession of the same types within the same areas -- Summary ofpreceding and present chapters.
Chapter XI(A,B, C)
Geographical Distribution
Present distribution cannot be accounted for by differences in physicalconditions -- Importance of barriers -- Affinity of the productions of thesame continent -- Centres of creation -- Means of dispersal, by changes ofclimate and of the level of the land, and by occasional means -- Dispersalduring the Glacial period co-extensive with the world.
Chapter XII(A,B)
Geographical Distribution -- continued
Distribution of fresh-water productions -- On the inhabitants of oceanicislands -- Absence of Batrachians and of terrestrial Mammals -- On therelation of the inhabitants of islands to those of the nearest mainland --On colonisation from the nearest source with subsequent modification --Summary of the last and present chapters.
Chapter XIII(A,B, C)
Mutual Affinities of Organic Beings:
Morphology: Embryology: Rudimentary Organs
Classification, groups subordinate to groups -- Natural system -- Rules anddifficulties in classification, explained on the theory of descent withmodification -- Classification of varieties -- Descent always used inclassification -- 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 sameindividual -- Embryology, laws of, explained by variations not superveningat an early age, and being inherited at a corresponding age -- RudimentaryOrgans; their origin explained -- Summary.
Chapter XIV(A,B)
Recapitulation and Conclusion
Recapitulation of the difficulties on 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 thetheory of natural selection may be extended -- Effects of its adoption onthe study of Natural history -- Concluding remarks.
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