Fig. 19.—The white lock of hair here shown is hereditary and has been traced back definitely through six generations; family tradition derives it from a son of Harry "Hot-Spur" Percy, born in 1403, and fallaciously assigns its origin to "prenatal influence" or "maternal impression." This young woman inherited the blaze from her father, who had it from his mother, who had it from her father, who migrated from England to America nearly a century ago. The trait appears to be a simple dominant, following Mendel's Law; that is, when a person with one of these locks who is a child of one normal and one affected parent marries a normal individual, half of the children show the lock and half do not. Photograph from Newton Miller.
