The most important general advance seems to be the recognition that the mind of the human adult is a social product; that it can only be understood in relation with the special environment in which it develops, and with which it is in perpetual interaction. Professor Baldwin, of Princeton, has done important work on this subject. Closely allied is the study of what is called ‘the psychology of groups,’ the laws of mental action of the individual as modified by his membership of some form of society. French authors have done valuable work here. These two developments of psychology are destined to provide the indispensable psychological basis for Social Science, and for the anthropological investigation of mental phenomena. Hereafter, the well-ascertained laws of experimental psychology will undoubtedly furnish the necessary scientific basis of the art of education, and psychology will hold the same relation to that art as physiology does to the art of medicine and hygiene. There can be little doubt, moreover, of the valuable interaction of the study of physical psychology and the theories of the origin of structural character by natural selection. The relation of the human mind to the mind of animals, and the gradual development of both, form a subject full of rich stores of new material, yielding conclusions of the highest importance, which has not yet been satisfactorily approached. I am glad to be able to give wider publicity here to some conclusions which I communicated to the Jubilee volume of the ‘Société de Biologie’ of Paris in 1899. I there discussed the significance of the great increase in the size of the cerebral hemispheres in recent, as compared with Eocene Mammals (see fig. 5), and in Man as compared with Apes, and came to the conclusion that ‘the power of building up appropriate cerebral mechanism in response to individual experience,’ or what may be called ‘educability,’ is the quality which characterizes the larger cerebrum, and is that which has led to its selection, survival, and further increase in volume. The bearing of this conception upon questions of fundamental importance in what has been called genetic psychology is sketched as follows: ‘The character which we describe as “educability” can be transmitted; it is a congenital character. But the _results_ of education can _not_ be transmitted. In each generation they have to be acquired afresh. With increased “educability” they are more readily acquired and a larger variety of them. On the other hand, the nerve-mechanisms of instinct are transmitted, and owe their inferiority as compared with the results of education to the very fact that they are _not_ acquired by the individual in relation to his particular needs, but have arisen by selection of congenital variation in a long series of preceding generations.’