In the case of elements of native origin, it is by imitation of the individuals of original powers of thought or feeling that the element becomes embodied in the national culture; in the case of foreign elements, by imitation of foreign models, acceptance of foreign ideas, through literature and personal contacts. In both cases, such general imitation will only take place when the culture-element in question is more or less congenial to the innate qualities of the bulk of individuals. All other novel elements will be ignored, or will fail to propagate themselves successfully; if they obtain a first footing, they will fail to pass beyond the stage of fashion into that of custom. And, when once accepted, the cultural element will usually undergo modification in the direction of more complete harmony with the innate tendencies; its less congenial features will be allowed to die out, its more congenial will be accentuated from generation to generation. The social environment of any civilised people is, then, very largely the result of a long continued process of selection, comparable with the natural selection by which, according to the Darwinian theory, animal species are evolved; a constant favouring of certain elements, a constant rejection of others. We may in fact regard each distinctive type of civilisation as a species, evolved largely by selection; and the selective agency, which corresponds to and plays a part analogous to the part of the physical environment of an animal species, is the innate mental constitution of the people. The sum of innate qualities is the environment of the culture-species, and it effects a selection among all culture variations, determining the survival and further evolution of some, the extermination of others. And, just as animal species (especially men) modify their physical environment in course of time, and also devise means of sheltering themselves from its selective influence, so each national life, each species of civilisation, modifies very gradually the innate qualities of the people and builds up institutions which, the more firmly they are established and the more fully they are elaborated, override and prevent the more completely the direct influence of innate qualities on national life.