London/ New York: Edward Arnold, 1896. First edition. Darwin's proposal of two sources of instinct--natural selection and inherited habit--fostered among late-nineteenth-century evolutionists a variety of conflicting notions concerning the mechanisms of evolution. Morgan, a British comparative psychologist, was a cardinal figure in restructuring the orthodox Darwinian conception to meet the demands of the new biology of Weismann. Illustrated. Ex-library copy with mostly minor markings (though rear endpaper is damaged). Top of spine has two small tears, still good to very good.