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Introduction
Chapter I: Variation Under Domestication. Causes of Variability
Effects of Habit and of the Use or Disuse of Parts; Correlated Variation; Inheritance
Character of Domestic Varieties; Difficulty of distinguishing between Varieties and Species; Origin of Domestic Varieties from one or more Species
Breeds of the Domestic Pigeon, their Differences and Origin
Principles of Selection anciently followed, and their Effects
Unconscious Selection
Circumstances favourable to Man's Power of Selection
Chapter II: Variation Under Nature
Individual Differences
Doubtful Species
Wide-ranging, much diffused, and common Species vary most
Species of the Larger Genera in each Country vary more frequently than the Species of the Smaller Genera
Many of the Species included within the Larger Genera resemble Varieties in being very closely, but unequally, related to each other, and in having restricted ranges
Summary
Chapter III: Struggle For Existence
The Term, Struggle for Existence, used in a large sense
Geometrical Ratio of Increase
Nature of the Checks to Increase
Complex Relations of all Animals and Plants to each other in the Struggle for Existence
Struggle for Life most severe between Individuals and Varieties of the same Species
Chapter IV: Natural Selection; Or the Survival of the Fittest
Sexual Selection
Illustrations of the Action of Natural Selection, or the Survival of the Fittest
On the Intercrossing of Individuals
Circumstances favourable for the production of new forms through Natural Selection
Extinction caused by Natural Selection
Divergence of Character
The Probable Effects of the Action of Natural Selection through Divergence of Character and Extinction, on the Descendants of a Common Ancestor
Convergence of Character
Summary of Chapter
Chapter V: Laws of Variation
Effects of the increased Use and Disuse of Parts, as controlled by Natural Selection
Acclimatisation
Correlated Variation
Compensation and Economy of Growth
Multiple, Rudimentary, and Lowly-organised Structures are Variable
A Part developed in any Species in an extraordinary degree or manner, in comparison with the same Part in allied Species, tends to be highly variable
Specific Characters more Variable than Generic Characters
Secondary Sexual Characters Variable
Chapter VI: Difficulties of the Theory
On the Absence or Rarity of Transitional Varieties
On the Origin and Transitions of Organic Beings with peculiar Habits and Structure
Organs of extreme Perfection and Complication
Modes of Transition
Special Difficulties of the Theory Of Natural Selection
Organs of little apparent Importance, as affected by Natural Selection
Utilitarian Doctrine, how far true: Beauty, how acquired
Summary: the Law of Unity of Type and of the Conditions of Existence embraced by the Theory of Natural Selection
Chapter VII: Miscellaneous Objections to the Theory of Natural Selection
Chapter VIII: Instinct
Inherited Changes of Habit or Instinct in Domesticated Animals
Special Instincts
Objections to the Theory of Natural Selection as applied to Instincts: Neuter and Sterile Insects
Summary
Chapter IX: Hybridism
Laws governing the Sterility of first Crosses and of Hybrids
Origin and Causes of the Sterility of first Crosses and of Hybrids
Reciprocal Dimorphism and Trimorphism
Fertility of Varieties when Crossed, and of their Mongrel Offspring, not universal
Hybrids and Mongrels compared, independently of their fertility
Summary of Chapter
Chapter X: On the Imperfection of the Geological Record
On the Lapse of Time, as inferred from the rate of Deposition and extent of Denudation
On the Poorness of Palaeontological Collections
On the Absence of Numerous Intermediate Varieties in any Single Formation
On the sudden Appearance of whole Groups of allied Species
On the Sudden Appearance of Groups of allied Species in the lowest known Fossiliferous Strata
Chapter XI: On the Geological Succession of Organic Beings
On Extinction
On the Forms of Life changing almost simultaneously throughout the World
On the Affinities of Extinct Species to each other, and to Living Forms
On the State of Development of Ancient compared with Living Forms
On the Succession of the same Types within the same Areas, during the later Tertiary periods
Summary of the preceding and present Chapters
Chapter XII: Geographical Distribution
Means of Dispersal
Dispersal during the Glacial Period
Alternate Glacial Periods in the North and South
Chapter XIII: Geographical Distribution Continued. Fresh-water Productions
On the Inhabitants of Oceanic Islands
Absence of Batrachians and Terrestrial Mammals on Oceanic Islands
On the Relations of the Inhabitants of Islands to those of the nearest Mainland
Summary of the last and present Chapters
Chapter XIV: Mutual Affinities of Organic Beings: Morphology: Embryology: Rudimentary Organs. Classification
Morphology
Development and Embryology
Rudimentary, Atrophied, and Aborted Organs
Summary
Chapter XV: Recapitulation and Conclusion
Glossary. Glossary of the Principal Scientific Terms Used In the Present Volume
Origin of Species
by Charles Darwin
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I will now say a few words on the circumstances, favourable, or the reverse, to man's power of selection. A high degree of variability is obviously favourable, as freely giving the materials for selection to work on; not that mere individual differences are not amply sufficient, with extreme care, to allow of the accumulation of a large amount of modification in almost any desired direction. But as variations manifestly useful or pleasing to man appear only occasionally, the chance of their appearance will be much increased by a large number of individuals being kept. Hence, number is of the highest importance for success. On this principle Marshall formerly remarked, with respect to the sheep of parts of Yorkshire, "as they generally belong to poor people, and are mostly in small lots, they never can be improved." On the other hand, nurserymen, from keeping large stocks of the same plant, are generally far more successful than amateurs in raising new and valuable varieties. A large number of individuals of an animal or plant can be reared only where the conditions for its propagation are favourable. When the individuals are scanty, all will be allowed to breed, whatever their quality may be, and this will effectually prevent selection. But probably the most important element is that the animal or plant should be so highly valued by man, that the closest attention is paid to even the slightest deviations in its qualities or structure. Unless such attention be paid nothing can be effected. I have seen it gravely remarked, that it was most fortunate that the strawberry began to vary just when gardeners began to attend to this plant. No doubt the strawberry had always varied since it was cultivated, but the slightest varieties had been neglected. As soon, however, as gardeners picked out individual plants with slightly larger, earlier, or better fruit, and raised seedlings from them, and again picked out the best seedlings and bred from them, then (with some aid by crossing distinct species) those many admirable varieties of the strawberry were raised which have appeared during the last half-century.
With animals, facility in preventing crosses is an important element in the formation of new races,- at least, in a country which is already stocked with other races. In this respect enclosure of the land plays a part. Wandering savages or the inhabitants of open plains rarely possess more than one breed of the same species. Pigeons can be mated for life, and this is a great convenience to the fancier, for thus many races may be improved and kept true, though mingled in the same aviary; and this circumstance must have largely favoured the formation of new breeds. Pigeons, I may add, can be propagated in great numbers and at a very quick rate, and inferior birds may be freely rejected, as when killed they serve for food. On the other hand, cats from their nocturnal rambling habits cannot be easily matched, and, although so much valued by women and children, we rarely see a distinct breed long kept up; such breeds as we do sometimes see are almost always imported from some other country. Although I do not doubt that some domestic animals vary less than others, yet the rarity or absence of distinct breeds of the cat, the donkey, peacock, goose, &c., may be attributed in main part to selection not having been brought into play: in cats, from the difficulty in pairing them; in donkeys, from only a few being kept by poor people, and little attention paid to their breeding; for recently in certain parts of Spain and of the United States this animal has been surprisingly modified and improved by careful selection: in peacocks, from not being very easily reared and a large stock not kept: in geese, from being valuable only for two purposes, food and feathers, and more especially from no pleasure having been felt in the display of distinct breeds; but the goose, under the conditions to which it is exposed when domesticated seems to have a singularly inflexible organisation, though it has varied to a slight extent, as I have elsewhere described.
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