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.

ON

THE ORIGIN OF SPECIES BY MEANS OF NATURAL SELECTION,

OR THE

PRESERVATION OF FAVOURED RACES IN THE STRUGGLE FOR LIFE.

BY CHARLES DARWIN, M.A., FELLOW OF THE ROYAL, GEOLOGICAL, LINNAEAN, ETC., SOCIETIES;

AUTHOR OF 'JOURNAL OF RESEARCHES DURING H.M.S. BEAGLE'S VOYAGE ROUND THE WORLD.'

LONDON:

JOHN MURRAY, ALBEMARLE STREET.

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.