The physical criteria of race, such as the colour of the skin, the hair, the shape of the skull, the odour of the glands, are well marked in the gross. I have examined their relative values for purposes of classification in another work, and need not repeat the details here. But the question is pertinent: Are there psychological distinctions separating the subspecies of man as clearly as those of his physical economy? Conflicting answers have been and still are offered to this inquiry. By some the mental powers of the races are asserted to be as sharply contrasted as their personal appearance, and the gulf between them to be practically impassable. I have already said that nothing in the minute or gross anatomy of the brain can be offered to support this view. The contributions to the general culture of the species have been markedly unequal; but may not this be explained by other reasons than inherent physical inequalities? I have already expressed the opinion that human groups have differed less in inherent psychical capacity than in stimuli and opportunities. Such, also, is the belief of that profound student of human development, Professor Bastian. He claims that convincing evidence in favour of such a view can be drawn from the uniformity in the development of thoughts, inventions, customs, religions, and the other elements of culture the world over, up to a certain point at which other intercurrent influences entered, not dependent on race distinctions. After a prolonged study of primitive peoples the anthropologist Waitz reached the conclusion that there is not and never was any positive difference in the intellectual power of races; and the historian Buckle, reviewing the record of the species in time, announced his conviction that “the natural faculties of man have made no progress.” In abundant instances the children of savage parents have been brought up in civilised surroundings and have shown themselves equal and occasionally superior to their comrades of the so-called higher race in all the tastes of cultured society. It were useless, therefore, to talk of an average natural inferiority. The attainment of a possible average, therefore, must be conceded. But this must not be construed as closing the question historically or psychically. It is constantly observed in education that children of equal ability are by no means equally good scholars. They respond differently to the stimulus of the desire of knowledge. Such contrasts are witnessed in races also, and, apart from whatever other influences we may name, are hereditary characteristics, recurring indefinitely and controlling the racial mind, its activities and its ambitions. So visible are the mental differences of races that some writers have advocated a psychological classification in anthropology. Professor Letourneau has attempted it in one of his many treatises.