ABSTRACT
The stream is heredity or animal transmission; the road is communication or social transmission. Heredity brings not only tendencies to a definite sort of physical development, but also capacity, aptitude, disposition, lines of teachability, or whatever else we may call the vague psychical tendencies that all of us are born with. Heredity and environment, as applied to the present life of a human being, are, in fact, abstractions; the real thing is a total organic process not separable into parts. Although the transmission of heredity through the germ-plasm is much the same in man as in the other animals, there is a notable difference in the kind of traits that are transmitted, and are found to exist at birth. The transmission of behavior through the germ-plasm is their test. Hence the disagreement as to the place of instinct in human life.
