Race feeling may be called prejudice by those whose careers are cramped by it, but it is a natural antipathy which serves to maintain the purity of type. The unfortunate fact that nearly all species of men interbreed freely leaves us no choice in the matter. Either the races must be kept apart by artificial devices of this sort, or else they ultimately amalgamate, and in the offspring the more generalized or lower type prevails.
The Passing of the Great Race (1916)