An Historical Sketch of the Progress of Opinion on the Origin of Species, Previously to the Publication of the First Edition of This Work
Author of the historical sketch and the Origin of Species; presents the progression of ideas leading to his own theory.
The Origin of Species by Means of Natural Selection
Author and primary narrator of the work, presenting his theory of natural selection.
I: Variation Under Domestication
Author and narrator, presenting his observations and conclusions on variation under domestication.
Causes of Variability
Author and primary narrator, presenting his observations and conclusions on variability.
Character of Domestic Varieties; Difficulty of Distinguishing Between Varieties and Species; Origin of Domestic Varieties from One or More Species
Author and narrator; presents his observations and conclusions on domestic varieties.
Breeds of the Domestic Pigeon, Their Differences and Origin
Author and narrator; presents his detailed study of domestic pigeons, their variations, and his argument for common descent from the rock-pigeon.
Unconscious Selection
Author and narrator, presenting the concept of unconscious selection and its role in domestic breeding.
Circumstances Favourable to Man’s Power of Selection
Author and narrator, presenting observations on artificial selection.
II: Variation Under Nature
Author and narrator; presents his views on variation, species definitions, and the importance of individual differences.
Doubtful Species
Author and narrator; presents his view that species and varieties are arbitrarily defined and that varieties are incipient species.
Species of the Larger Genera in Each Country Vary More Frequently Than the Species of the Smaller Genera
Author and narrator, presenting statistical tables and reasoning on variation in larger versus smaller genera.
III: Struggle for Existence
Author and narrator, presents the concept of struggle for existence and natural selection.
The Term, Struggle for Existence, Used in a Large Sense
Author and narrator, defining the term 'struggle for existence' in a large and metaphorical sense.
Geometrical Ratio of Increase
Author and narrator; presents calculations and observations on population increase.
Complex Relations of All Animals and Plants to Each Other in the Struggle for Existence
Author and observer; recounts personal investigations on a Staffordshire heath and near Farnham, and experiments with Lobelia fulgens and clover.
Natural Selection; or the Survival of the Fittest
Author and primary narrator; introduces and defends the concept of natural selection.
Sexual Selection
Author and primary voice; introduces and explains the theory of sexual selection.
Illustrations of the Action of Natural Selection, or the Survival of the Fittest
Author and narrator, presents imaginary illustrations and discusses the action of natural selection.
On the Intercrossing of Individuals
Author and narrator; presents his own experiments and observations on cross-fertilization.
Circumstances Favourable for the Production of New Forms Through Natural Selection
Author and narrator; presents his reasoning on the factors favoring natural selection.
Extinction Caused by Natural Selection
Author and narrator, presenting the argument that natural selection causes extinction.
The Probable Effects of the Action of Natural Selection Through Divergence of Character and Extinction, on the Descendants of a Common Ancestor
Author presenting the theoretical model of divergence and extinction.
Summary of Chapter
Author and narrator of the summary, presenting the core arguments for natural selection.
V: Laws of Variation
Author and narrator; presents his arguments on the laws of variation.
Effects of the Increased Use and Disuse of Parts, as Controlled by Natural Selection
Author and narrator; presents arguments and observations on use and disuse.
Acclimatisation
Author of the chapter, presenting arguments and observations on acclimatisation.
Secondary Sexual Characters Variable
Author presenting the argument on variability of secondary sexual characters and their relation to species differences.
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
Author and narrator, presenting evidence for analogous variation and reversion.
VI: Difficulties of the Theory
Author and narrator, presenting and defending his theory against difficulties.
On the Absence or Rarity of Transitional Varieties
Author and primary narrator, presenting his theory and addressing difficulties.
On the Origin and Transition of Organic Beings with Peculiar Habits and Structure
Author and narrator, presenting arguments and observations on transitional habits and structures.
Organs of Extreme Perfection and Complication
Author and primary voice, defending natural selection against the objection of complex organs.
Modes of Transition
Author and primary voice, presenting arguments for transitional modes and defending his theory.
Special Difficulties of the Theory of Natural Selection
Darwin presents and defends his theory against difficulties, arguing that apparent obstacles can be explained by natural selection acting on slight variations over long periods.
Organs of Little Apparent Importance, as Affected by Natural Selection
Author and narrator, reflecting on the difficulty of understanding the origin of organs of little apparent importance and cautioning against over-attributing characters to natural selection.
Utilitarian Doctrine, How Far True: Beauty, How Acquired
Author and primary voice defending the utilitarian doctrine and explaining the role of natural and sexual selection in producing beauty.
The Law of Unity of Type and of the Conditions of Existence Embraced by the Theory of Natural Selection
Author and narrator, presenting and defending the theory of natural selection against objections.
Instinct
Author and narrator; presents the argument that instincts evolve through natural selection and addresses the difficulty of sterile neuter insects.
Inherited Changes of Habit or Instinct in Domesticated Animals
Author and observer, presents personal observations of pointing dogs and tumbler pigeons.
Special Instincts
Author and narrator, analyzing instincts through natural selection.
Instincts of the Cuckoo
Author and narrator, presents the argument for natural selection of cuckoo instincts.
Slave-Making Instinct
Conducted detailed observations of Formica sanguinea nests in Surrey and Sussex, including witnessing a migration and slave-making raids.
Objections to the Theory of Natural Selection as Applied to Instincts: Neuter and Sterile Insects
Author and narrator; presents and defends the theory of natural selection against objections regarding instincts and neuter insects.
Summary
Author summarizing his arguments on instinct and natural selection.
IX: Hybridism
Author of the chapter, presenting his argument that sterility of crosses is not due to natural selection.
Laws Governing the Sterility of First Crosses and of Hybrids
Darwin presents his argument that sterility is incidental, not specially endowed, using examples from grafting and crossing.
Origin and Causes of the Sterility of First Crosses and of Hybrids
Author and primary voice, presenting arguments against natural selection as the cause of hybrid sterility.
Reciprocal Dimorphism and Trimorphism
Author and primary investigator; conducted experiments on dimorphic and trimorphic plants over four years.
Fertility of Varieties When Crossed, and of Their Mongrel Offspring, Not Universal
Author presenting the argument that fertility does not distinguish varieties from species.
On the Imperfection of the Geological Record
Author and narrator; defends his theory against the objection of missing transitional forms.
On the Lapse of Time, as Inferred from the Rate of Deposition and Extent of Denudation
Author and narrator, presenting geological evidence for the vastness of time.
On the Absence of Numerous Intermediate Varieties in Any Single Formation
Author and narrator; presents arguments on the imperfection of the geological record and the rarity of intermediate fossil varieties.
On the Sudden Appearance of Groups of Allied Species in the Lowest Known Fossiliferous Strata
Author; argues for vast pre-Cambrian periods and the imperfection of the geological record.
On the Geological Succession of Organic Beings
Author and narrator; reflects on his own astonishment at extinction and interprets the geological record in light of natural selection.
On Extinction
Author and narrator; reflects on his own astonishment at extinction and his findings in La Plata.
On the Forms of Life Changing Almost Simultaneously Throughout the World
Author presenting the theory of natural selection to explain the simultaneous change of life forms.
On the Affinities of Extinct Species to Each Other, and to Living Forms
Author presenting the theory of descent with modification to explain affinities between extinct and living species.
On the State of Development of Ancient Compared with Living Forms
Author and narrator, presenting arguments on the advancement of organization through natural selection.
On the Succession of the Same Types Within the Same Areas, During the Later Tertiary Periods
Author who strongly insisted on the 'law of the succession of types' in 1839 and 1845, and explains it via descent with modification.
Geographical Distribution
Author and narrator; presents the argument for single centres of creation and subsequent migration.
Freshwater Productions
Describes his own observations and experiments, including collecting in Brazil and suspending duck feet in an aquarium.
Absence of Batrachians and Terrestrial Mammals on Oceanic Islands
Author and narrator; conducts experiments on land-shell immersion and synthesizes observations on island biogeography.
On the Relations of the Inhabitants of Islands to Those of the Nearest Mainland
Author and narrator; presents observations and arguments on island biogeography.
Analogical Resemblances
Author and narrator, presenting the argument on analogical resemblances and natural selection.
Development and Embryology
Author and narrator; presents the argument and evidence for embryological development as supporting common descent.
Rudimentary, Atrophied, and Aborted Organs
Author and primary narrator; presents the argument that rudimentary organs are remnants of ancestral states.
Summary
Author and narrator summarizing the chapter's arguments on classification, morphology, embryology, and rudimentary organs.
Recapitulation and Conclusion
Author and narrator, presenting the recapitulation and conclusion of his theory.
