"Everyone who believes in the higher evolution of living organisms must admit that every manifestation of the vital urge and struggle to live must have had a definite beginning in time and that one subject alone must have manifested it for the first time. It was then repeated again and again; and the practice of it spread over a widening area, until finally it passed into the subconscious of every member of the species, where it manifested itself as 'instinct.'"