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The Origin of Species
by Charles Darwin
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Chapter I. Variation Under Domestication
Causes of Variability
Effects of Habit and 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, 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 of the larger genera resemble varieties in being very closely, but unequally, related to each other, and in having restricted ranges.
Chapter III. Struggle for Existence
Its bearing on natural selection
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
Natural Selection
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
On the degree to which Organisation tends to advance
Convergence of character
Chapter V. Laws of Variation
Effects of changed conditions
Effects of the increased use and disuse of parts, as controlled by Natural Selection
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
Distinct species present analogous variations, so that a variety of one species often assumes a character proper to an allied species, or reverts to some of the characters of an early progenitor
Chapter VI. Difficulties of the Theory
Difficulties of the theory of descent with modification
Absence or rarity of transitional varieties
On the origin and transition 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
Chapter VII
Miscellaneous Objections to the Theory of Natural Selection
Chapter VIII. Instinct
Instincts comparable with habits, but different in their origin
Inherited changes of habit or instinct in domesticated animals
Special instincts; Instincts of the cuckoo
Slave-making instinct
Cell-making instinct of the hive-bee
Objections to the theory of natural selection as applied to instincts: neuter and sterile insects
Chapter IX. Hybridism
Distinction between the sterility of first crosses and of hybrids
Degrees of sterility
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 absence of intermediate varieties at the present day
On the lapse of time, as inferred from the rate of denudation and of deposition
On the poorness of our 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 the slow and successive appearance of new species
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 species
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 preceding and present chapter
Chapter XII. Geographical Distribution
Present distribution cannot be accounted for by differences in physical conditions
Single centres of supposed creation
Means of dispersal
Dispersal during the Glacial period
Alternate Glacial periods in the north and south
Chapter XIII. Geographical Distribution -- continued
Distribution of fresh-water productions
On the inhabitants of oceanic islands
Absence of Batrachians and terrestrial Mammals on oceanic islands
On the relation of the inhabitants of islands to those of the nearest mainland
Summary of the last and present chapter
Chapter XIV. Mutual Affinities of Organic Beings: Morphology -- Embryology -- Rudimentary Organs
Analogical resemblances
On the nature of the affinities connecting organic beings
Development and embryology
Rudimentary, atrophied, and aborted organs
Chapter XV
Recapitulation and Conclusion
Glossary of Scientific Terms

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