"Heredity is not the dark specter which some people have thought—merciless and unchangeable, the embodiment of Fate itself. This dark, pessimistic belief which tinges even the literature of to-day comes, no doubt, from the general lack of knowledge of the laws governing the interaction of these two ever-present forces of heredity and environment wherever there is life. My own studies have led me to be assured that heredity is only the sum of all past environment, in other words environment is the architect of heredity; and I am assured of another fact: acquired characters are transmitted and—even further—that all characters which are transmitted have been acquired..."