The Foundations of the Origin of Species Two Essays written in 1842 and 1844 · Charles Darwin
Chapter 1
Sec. iii. On variation in instincts and other mental attributes 17 Sec.Sec. iv. and v. On the evidence from Geology. (The reasons for combining the two sections are given in the Introduction) 22 Sec. vi. Geographical distribution 29 Sec. vii. Affinities and classification 35 Sec. viii. Unity of type in the great classes 38 Sec. ix. Abortive organs 45 Sec. x. Recapitulation and conclusion 48 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 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 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 ON THE EVIDENCE FAVOURABLE AND OPPOSED TO THE VIEW THAT SPECIES ARE NATURALLY FORMED RACES, DESCENDED FROM COMMON STOCKS. ON THE NUMBER OF INTERMEDIATE FORMS REQUIRED ON THE THEORY OF COMMON DESCENT; AND ON THEIR ABSENCE IN A FOSSIL STATE Gradual appearance of species Extinction of species ON THE GEOGRAPHICAL DISTRIBUTION OF ORGANIC BEINGS IN PAST AND PRESENT TIMES. Distribution of the inhabitants in the different continents Relation of range in genera and species Distribution of the inhabitants in the same continent Insular Faunas Alpine Floras Cause of the similarity in the floras of some distant mountains Whether the same species has been created more than once On the number of species, and of the classes to which they belong in different regions SECOND SECTION 174-182 Geographical distribution of extinct organisms Changes in geographical distribution Summary on the distribution of living and extinct organic beings An attempt to explain the foregoing laws of geographical distribution, on the theory of allied species having a common descent Improbability of finding fossil forms intermediate between existing species ON THE NATURE OF THE AFFINITIES AND CLASSIFICATION OF ORGANIC BEINGS.
Text from Project Gutenberg, public domain in the United States.