The subject of heredity in relation to the mental evolution of the race and to mental disease is of such supreme importance that I plead no excuse for making it the subject of my paper. It is a subject which has not in the past received that amount of attention from us as alienists which its momentous-ness demands. But the work of Galton, the revivified monumental experiments of Mendel, and the investigations of the school of biometricians, headed by Karl Pearson, have latterly given a great impetus to this line of study.