- §§ iv. and v. On the evidence from Geology. (The reasons for combining the two sections are given in the Introduction) [22]
- § vi. Geographical distribution [29]
- § vii. Affinities and classification [35]
- § viii. Unity of type in the great classes [38]
- § ix. Abortive organs [45]
- § x. Recapitulation and conclusion [48]
ESSAY OF 1844
PART I
CHAPTER I
ON THE VARIATION OF ORGANIC BEINGS UNDER DOMESTICATION; AND ON THE PRINCIPLES OF SELECTION.
- Variation
- On the hereditary tendency
- Causes of Variation
- On Selection
- Crossing Breeds
- Whether our domestic races have descended from one or more wild stocks
- Limits to Variation in degree and kind
- In what consists Domestication
- Summary [57]-[80]
CHAPTER II
ON THE VARIATION OF ORGANIC BEINGS IN A WILD STATE; ON THE NATURAL MEANS OF SELECTION; AND ON THE COMPARISON OF DOMESTIC RACES AND TRUE SPECIES.
- Variation
- Natural means of Selection
- Differences between “Races” and “Species”:—first, in their trueness or variability
- Difference between “Races” and “Species” in fertility when crossed
- Causes of Sterility in Hybrids
- Infertility from causes distinct from hybridisation
- Points of Resemblance between “Races” and “Species”
- External characters of Hybrids and Mongrels
- Summary
- Limits of Variation [81]-[111]
CHAPTER III
ON THE VARIATION OF INSTINCTS AND OTHER MENTAL ATTRIBUTES UNDER DOMESTICATION AND IN A STATE OF NATURE; ON THE DIFFICULTIES IN THIS SUBJECT; AND ON ANALOGOUS DIFFICULTIES WITH RESPECT TO CORPOREAL STRUCTURES.
- Variation of mental attributes under domestication
- Hereditary habits compared with instincts
- Variation in the mental attributes of wild animals
- Principles of Selection applicable to instincts
- Difficulties in the acquirement of complex instincts by Selection
- Difficulties in the acquirement by Selection of complex corporeal structures [112]-[132]