It may still be said, however, that in selecting an example from so highly organized an animal as a bird, we are taking for granted that a complex case of controlled behaviour may fairly be accepted as a type of more simple cases. Unfortunately the only being with whose power of conscious control we have any first-hand acquaintance is possessed of a nervous system even more complex than that of the chick. Our psychological interpretations are inevitably anthropomorphic. All we can hope to do is to reduce our anthropomorphic conclusions to their simplest expression. The irreducible residuum seems to be that wherever an animal, no matter how lowly its station in the scale of life, profits by experience, and gives evidence of association, it must have some dim remembrance, or, let us now say, some re-presentation, of the results of previous behaviour which enters into and remodels the conscious situation; that through the re-presentative elements behaviour is somehow guided; and, further, that the centre of conscious control is different from the centre of response over which the control is exercised. II.--THE EARLY STAGES OF MENTAL DEVELOPMENT We use the phrase “mental development” in its broadest acceptation as inclusive of, and applicable to, all phases of effective consciousness. We shall assume that throughout this development there is a concomitant development of nerve-centres and of their organic connections. And we shall further assume that experience, as such, is not inherited.