Such facts are certainly not in favour of the prevalent theory that the differences of race are due to direct adaptation. Whether Professor Weismann’s theory proves to be well founded or not, we manifestly cannot assume that the heredity of acquired characters suffices to explain the origin of the human races. It seems most probable that, at the very earliest stages of human evolution, mankind was restricted to a comparatively small area, and was then homogeneous, as every animal and vegetable species is under similar conditions. In the struggle for existence the intellectual faculties of man were developed, and before the breaking away of isolated groups he may have invented the art of making fire, and of fabricating the simplest implements and weapons. This mental superiority made it possible for man to disperse, enabling him to exist even under conditions somewhat different from those to which he was originally adapted. His organism had to undergo certain changes, but we are not aware that these modifications were transmitted to descendants. All that we know is, that the children born were not exactly like each other, and that those who happened to vary most in accordance with the new conditions of life as a rule survived, and became the ancestors of following generations. The congenital characters which enabled them to survive were of course transmitted to their offspring, and thus, through natural selection,[1613] races would gradually arise, the members of each of which would have as hereditary dispositions the same peculiarities as those which, to a certain extent, may be acquired through acclimatization, but then only for the individual himself, not for his descendants. We can thus understand how the children of a negro are black[1614]—even if they are born in Europe[1615]—as the black colour is the correlative of certain physiological processes favourable to existence in the country of their race. They survive, whilst the children of Europeans who have emigrated to the tropics are carried off in great numbers, even though their parents have succeeded in undergoing the functional modifications which accompanied the change of abode. This explanation of racial differences seems the more acceptable, when we take into consideration the immense period which has elapsed since man began to spread over the earth, and the slow and gradual change of abodes. He was not at once moved from the tropics to the polar zones, or from the polar zones to the tropics, but had to undergo an indefinitely long chain of adaptive processes. Thus were gradually established such radical differences as those which distinguish a European from a negro, an Australian from a Red-skin. * * * * *