On the Variation of Species, with Especial Reference to the Insecta

Nor is this dependency on external circumstances less apparent in the animal kingdom also,--the domesticated races of which every agriculturist is aware are capable of modification, artificially, to an almost unlimited extent; and which exhibit, when even in a state of nature, nearly as great a variety, from purely natural causes, as they have been proved to do when subjected to the laws and routine of agrarian science. Take the sheep, for example, of Dartmoor or Wales, and compare them with those from the wolds of Lincolnshire and th