The Foundations of the Origin of Species Two Essays written in 1842 and 1844
CHAPTER II 81-111
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