Origin of Species by Means of Natural Selection,

or the Preservation of Favored Races in the Struggle for Life

Charles Darwin

6th Edition, 1872

Table of Contents

Volume I

Additions and Corrections, to the Sixth Edition

Historical Sketch 2


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--Domestic Pigeons, their Differences and Origin--Principles of Selection anciently followed, their Effects--Methodical and Unconscious Selection--Unknown Origin of our Domestic Productions--Circumstances favorable 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 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--[Summary]

Chapter III: Struggle for Existence

Its bearing on natural selection--The term used in a wide sense--Geometrical ratio of increase--Rapid increase of naturalized 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; or The Survival of the Fittest

Natural Selection: its power compared with man's selection; its power on characters of trifling importance; its power at all ages and Oil both sexes--Sexual Selection--On the generality of intercrosses between individuals of the same species--Circumstances favorable and unfavorable to the results of 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 naturalization--Action of Natural Selection, through Divergence of Character, and Extinction, on the descendants from a common parent--Explains the grouping of all organic beings--Advance in organization--Low forms preserved--Convergence of character--Indefinite multiplication of species--Summary

Chapter V: Laws of Variation

Effects of changed conditions--Use and disuse, combined with natural selection; organs of flight and of vision--Acclimatization--Correlated Variation--Compensation and economy of growth--False correlations--Multiple, rudimentary, and lowly organized 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 of the Theory

Difficulties of the theory of descent with modification--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--Modes 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: Miscellaneous Objections to the Theory of Natural Selection 3

Longevity--Modifications not necessarily simultaneous---Modifications apparently of no direct service--Progressive development--Characters of small functional importance, the most constant--Supposed incompetence of natural selection to account for the incipient stages of useful structures--Causes which interfere with the acquisition through natural selection of useful structures--Gradations of structure with changed functions--Widely different organs in members of the same class, developed from one and the same source--Reasons for disbelieving in great and abrupt modifications

Chapter VIII: 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, molothrus, ostrich, and parasitic bees--Slave-making ants--Hive-bee, its cellmaking instinct--Changes of instinct and structure not necessarily simultaneous--Difficulties of the theory of the Natural Selection Of instincts--Neuter or sterile insects--Summary

Volume II

Chapter IX: 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, not accumulated by natural selection--Causes of the sterility of first crosses and of hybrids--Parallelism between the effects of changed conditions of life and of crossing--Dimorphism and trimorphism--Fertility of varieties when crossed and of their mongrel offspring not universal--Hybrids and mongrels compared independently of their fertility--Summary

Chapter X: 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 lapse of time, as inferred from the rate of denudation and of deposition--On the lapse of time as estimated by years--On the poorness of our paleontological collections--On the intermittence of geological formations--On the denudation of granitic areas--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--Antiquity of the habitable earth .

Chapter XI: 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 XII: 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--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 of terrestrial Mammals--On the relation of the inhabitants of islands to those of the nearest mainland--On colonization from the nearest source with subsequent modification--Summary of the last and present chapters

Chapter XIV: 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 XV: Recapitulation and Conclusion

Recapitulation of the objections to the theory of Natural Selection--Recapitulation of the general and special circumstances in its favor--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

Glossary of Scientific Terms 4