One additional point of our inquiry into the organic basis of mental activity remains to be investigated; namely, the question, Has the organic basis for the faculty of man been improved by civilization, and particularly may that of primitive races be improved by this agency? We must consider both the anatomical and the psychological aspects of this question. I have already pointed out that civilization causes anatomical changes of the same description as those accompanying the domestication of animals. It is likely that changes of mental character go hand in hand with them. The observed anatomical changes are, however, limited to this group of phenomena. We cannot prove that any progressive changes of the human organism have taken place; and particularly no advance in the size or complexity of the structure of the central nervous system, caused by the cumulative effects of civilization, can be proved. The difficulty of proving a progress of faculty is still greater. It seems to me that the probable effect of civilization upon an evolution of human faculty has been much overestimated. The psychical changes which are the immediate consequence of domestication or civilization may be considerable. They are changes due to the influence of environment. It is doubtful, however, if any progressive changes, or such as are transmitted by heredity, have taken place. The number of generations subjected to this influence seems altogether too small. For large portions of Europe we cannot assume more than forty or fifty generations; and even this number is probably considerably too high, inasmuch as in the middle ages the bulk of the population lived on very low stages of civilization. Besides this, the tendency of human multiplication is such, that the most highly cultured families tend to disappear, while others which have been less subjected to the influences regulating the life of the most cultured class take their place. Therefore it is much less likely that advance is hereditary than that it is transmitted by means of education.