greater quantity of energy in which this greater mental mass shows itself. Hence a series of inquiries, of which these are some: (a.) What is the relation between mental mass and bodily mass? Manifestly, the small races are deficient in it. But it also appears that races much upon a par in size—as, for instance, an Englishman and a Damara—differ considerably in mental mass, (b.) What is its relation to mass of brain? and, bearing in mind the general law that, in the same species, size of brain increases with size of body (though not in the same proportion), how far can we connect the extra mental mass of the higher races with an extra mass of brain beyond that which is proper to their greater bodily mass? (c.) What relation, if any, is there between mental mass and the physiological state expressed in vigor of circulation and richness of blood, as severally determined by mode of life and general nutrition? (d.) What are the relations of this trait to the social state, as predatory or industrial, nomadic or agricultural?
2. Mental Complexity.—How races differ in respect of the more or less involved structures of their minds will best be understood, on recalling that unlikeness between the juvenile mind and the adult mind among ourselves which so well typifies the unlikeness between the minds of savage and civilized. In the child we see absorption in special facts. Generalities even of a low order are scarcely recognized; and there is no recognition of high generalities. We see interest in individuals, in personal adventures, in domestic affairs; but no interest in political or social matters. We see vanity about clothes and small achievements; but little sense of justice: witness the forcible appropriation of one another's toys. While there have come into play many of the simpler mental powers, there has not yet been reached that complication of mind which results from the addition of powers evolved out of these simpler ones. Kindred differences of complexity exist between the minds of lower and higher races; and comparisons should be made to ascertain their kinds and amounts. Here, too, there may be a subdivision of the inquiries: (a.) What is the relation between mental complexity and mental mass? Do not the two habitually vary together? (b.) What is the relation to the social state, as more or less complex?—that is to say. Do not mental complexity and social complexity act and react on each other?
3. Rate of Mental Development.—In conformity with the biological law, that the higher the organisms the longer they take to evolve, members of the inferior human races may be expected to complete their mental evolution sooner than members of the superior races; and we have evidence that they do this. Travelers from all regions comment, now on the great precocity of children among savage and semi-civilized peoples, and now on the early arrest of their mental progress. Though we scarcely need more proofs that this general contrast exists, there remains to be asked the question, whether it is
