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Title:  On the Origin of Species

Author:  Charles Darwin

Release Date:  March, 1998 [EBook #1228]
[This file was last updated on February 2, 2003]

Edition:  11

Language:  English

Character set encoding:  ASCII

*** START OF THE PROJECT GUTENBERG EBOOK ON THE ORIGIN OF SPECIES ***

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ON THE

ORIGIN OF SPECIES.

“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.

CONTENTS.

INTRODUCTION.

CHAPTER 1.  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 2.  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 3.  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 4.  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 5.  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 6.  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 7.  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 8.  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 9.  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 10.  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 11.  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 12.  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 13.  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 14.  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 the theory of natural selection may be extended. 
Effects of its adoption on the study of Natural history. 
Concluding remarks.