its fullest sense, is the larger concept, and includes both inertia and divergence, both continuance and change. Whatever be the terms used, there are two complemental facts: that like tends to beget like, yet that every new creature has in some way an individuality of its own."[1] Both these truths are illustrated by the fact of common experience that the child is like its parents in some respects, and differs from them in others.
§3. The Principle of Stability. The principle that like tends to beget like is responsible for the fundamental identity of humanity from one generation to another. The biologist explains why like tends to beget like by the theory of the "germ-plasm." The part that the germ-plasm plays in securing the similarity of one generation to the next has been well explained by Weismann. "In development," he says, "a part of the germ-plasm contained in the parent egg-cell is not used up for the construction of the body of the offspring, but is reserved unchanged for the formation of the germ-cells of the following generation." Certain germ-cells are specially set aside to perform the function of reproduction. These cells have not been exhausted in body-building, but have preserved intact the full inheritance which the individual has received, ready to be passed on to the succeeding generation. Thus, as Professor J. Arthur Thomson says, "The parent is rather the trustee of the germ-plasm than the producer of the child."
This undying germ-plasm supplies the principle of continuity from one generation to the next. It
