On the Origin of Species
by Charles Darwin
'But with regard to the material world, we can at least go so far as this--
we can perceive that events are brought about not by insulated
interpositions of Divine power, exerted in each particular case, but by the
establishment of general laws.'
W. Whewell: Bridgewater Treatise.
'To conclude, therefore, let no man out of a weak conceit of sobriety, or
an ill-applied moderation, think or maintain, that a man can search too far
or be too well studied in the book of God's word, or in the book of God's
works; divinity or philosophy; but rather let men endeavour an endless
progress or proficience in both.'
Bacon: Advancement of Learning.
Down, Bromley, Kent,
October 1st, 1859.
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
Variation under Domestication
Causes of Variability -- Effects of Habit -- Correlation of Growth --
Inheritance -- 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 -- Principle of Selection anciently followed, its Effects --
Methodical and Unconscious Selection -- Unknown Origin of our Domestic
Productions -- 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 genera
in any 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.
Chapter III
Struggle for Existence
Bears on natural selection -- The term used in a wide sense -- Geometrical
powers 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
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.
Chapter V
Laws of Variation
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.
Chapter VI
Difficulties on Theory
Difficulties on the theory of descent with modification -- Transitions --
Absence 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
-- 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 the
theory of Natural Selection.
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 -
- Difficulties on the theory of the Natural Selection of instincts --
Neuter or sterile insects -- Summary.
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 -- 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 not
universal -- Hybrids and mongrels compared independently of their fertility
-- Summary.
Chapter IX
On the Imperfection of the Geological Record
On the absence of intermediate varieties at the present day -- On the
nature of extinct intermediate varieties; on their number -- On the vast
lapse of time, as inferred from the rate of deposition and of denudation --
On the poorness of our palaeontological collections -- On the intermittence
of geological formations -- On the absence of intermediate varieties in any
one formation -- On the sudden appearance of groups of species -- On their
sudden appearance in the lowest known fossiliferous strata.
Chapter X
On the Geological Succession of Organic Beings
On the slow and successive appearance of new species -- On their different
rates of change -- Species once lost do not reappear -- Groups of species
follow the same general rules in their appearance and disappearance as do
single species -- On Extinction -- On simultaneous changes in the forms of
life throughout the world -- On the affinities of extinct species to each
other and to living species -- On the state of development of ancient forms
-- On the succession of the same types within the same areas -- Summary of
preceding and present chapters.
Chapter XI
Geographical Distribution
Present distribution cannot be accounted for by differences in physical
conditions -- Importance of barriers -- Affinity of the productions of the
same continent -- Centres of creation -- Means of dispersal, by changes of
climate and of the level of the land, and by occasional means -- Dispersal
during the Glacial period co-extensive with the world.
Chapter XII
Geographical Distribution -- continued
Distribution of fresh-water productions -- On the inhabitants of oceanic
islands -- Absence of Batrachians and of terrestrial Mammals -- On the
relation 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
Mutual Affinities of Organic Beings:
Morphology: Embryology: Rudimentary Organs
Classification, groups subordinate to groups -- Natural system -- Rules and
difficulties in classification, explained on the theory of descent with
modification -- Classification of varieties -- Descent always used in
classification -- 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 same
individual -- Embryology, laws of, explained by variations not supervening
at an early age, and being inherited at a corresponding age -- Rudimentary
Organs; their origin explained -- Summary.
Chapter XIV
Recapitulation and Conclusion
Recapitulation of the difficulties on the theory of Natural Selection --
Recapitulation of the general and special circumstances in its favour --