Racial Heredity as a Factor in Social Evolution.--We have already seen that racial heredity is the most important and at the same time the least known factor in the problem of immigration. While there is still much disagreement among scientific men as to the importance of racial heredity in social problems, it can be said that the weight of opinion inclines to the view that racial heredity is a very real factor, and one which cannot be left altogether out of account in studying social problems. The view of Buckle that racial heredity counted for nothing in explaining the social life of various peoples is not upheld by modern biologists. On the contrary the biological view would emphasize the importance of species and racial heredity in all problems connected with life; thus no one denies that between different species of animals heredity counts for everything in explaining their life activities, and, as between the different breeds or races of a single species, no other position is possible from the biological point of view. Nevertheless it may be admitted that man no longer lives a purely animal life and that racial heredity as a factor in his social life may be easily exaggerated. On the whole, it is a safe rule to follow that racial heredity should not be invoked to explain the social condition of a people until practically all other factors have been exhausted. Nevertheless as between the different races or great varieties of mankind there must be a great difference in racial heredity. It could not, indeed, be otherwise, since these different races were developed in different geographical environments or "areas of characterization." Natural selection has developed in each race of mankind an innate character fitted to cope with the environment in which it was evolved. This is clearly perceptible in regard to their bodily traits, and all modern research seems to show that their native reactions to different stimuli also vary greatly, that is, heredity affects their thoughts, feelings and mode of conduct as well as the color of skin, texture of hair, and shape of head. In other words, the instincts or native reactions of the different races of man vary considerably in degree if not in quality, and from this it follows that their feelings, ideas, and modes of conduct must also vary considerably. It may be noted, however, that taking racial heredity into full account by no means leads to an attitude of fatalism as regards racial problems. On the contrary modern biology clearly teaches that racial heredity is modifiable both in the individual and in the race. It is modifiable in the individual through education or training; it is modifiable in the race through selection. Therefore racial heredity does not foredoom any people to remain in a low status of culture; only it must be taken into account in explaining the cultural conditions of all peoples, and especially in planning for a people's social amelioration.