This is the third book that Professor Wheeler has turned out in a relatively short time, the former ones being the “Science of Psychology “and “Readings in Psychology.” All of these books deal with man from an organismic point of view. They consider him as a biological unit, functioning in a social environment, and like all biological units, he considers him from the point of view of the organism-as-a-whole. This books deals with man from this point of view, considering Child's ‘physiological gradients’ and Coghill's ‘differentiation’ from an undifferentiated background as being the method of evolution rather than an addative process of building up reflex arcs. The particular characteristics in which this book differs from its predecessors is that it is devoted