“animals distinguish in the environment, and treat as a separate thing, whatever portion of matter appeals to their peculiar instincts, and affords occasion for their characteristic modes of activity.” And this differentiation of specially interesting things from each other, and from their relatively uninteresting surroundings, must be accompanied by some differentiation of these things from themselves as affected by them and reacting to them. So that here, as we have seen to be the case in other matters, what is commonly called the perceptual life of animals affords the rough-hewn materials from which ideal constructions may be elaborated by rational beings. We cannot here attempt to do more than barely indicate the manner in which the perceptual process in animals may acquire unity and diversity--unity through the functioning of the same brain and body, diversity from the different modes of functioning and the differential effects of diverse modes of stimulation. The interesting point for us in our special inquiry is that it is through behaviour that all this is brought about. As we interpret the facts, the restless activity of the young is primarily a biological fact, and is to be dealt with as an organic problem--a complication of the fundamental irritability of protoplasm. But it is also an essential condition to the acquisition of conscious experience; and the more there is of it in varied modes the wider is the range of the data afforded to consciousness. Congenital behaviour is thus the goal of organic heredity, and the starting-point of conscious accommodation and adjustment; it is the biological end of variation, and affords the means to intelligent modification.