It would be saying too much to claim that all the distinct European types become the same in America, without mixture, solely by the action of the new environment. First of all, I have investigated only the effect of one environment, and there is every reason to believe that a number of distinct types are developing in America; but we will set aside this point, and discuss only our New York observations. Although the long-headed Sicilian becomes more round-headed in New York, the round-headed Bohemian and Hebrew more long-headed, the approach to a uniform general type cannot be established, because we do not know yet how long the changes continue, and whether they would all lead to the same result. I confess, I do not consider such a result as likely, because the proof of the plasticity of types does not imply that the plasticity is unlimited. The history of the British types in America, of the Dutch in the East Indies, of the Spaniards in South America, favors the assumption of a strictly limited plasticity. Certainly our discussion should be based on this more conservative basis until an unexpectedly wide range of variability of types can be proved. It is one of the most important problems that arise out of this investigation, to determine how far the instability or plasticity of types may extend. Whatever the extent of these bodily changes may be, if we grant the correctness of our inferences in regard to the plasticity of human types, we are necessarily led to grant also a great plasticity of the mental make-up of human types. We have observed that features of the body which have almost obtained their final form at the time of birth show modifications of great importance in new surroundings. We have seen that others which increase during the whole period of growth, and are therefore subject to the continued effect of the new environment, are modified even among individuals who arrived here during their childhood. From these facts we must conclude that the fundamental traits of the mind, which are closely correlated with the physical condition of the body, and whose development continues over many years after physical growth has ceased, are the more subject to far-reaching changes. It is true that this is a conclusion by inference; but if we have succeeded in proving changes in the form of the body, the burden of proof will rest on those who, notwithstanding those changes, continue to claim the absolute permanence of other forms and functions of the body. In order to gain a correct understanding of the importance of changes in the frame of the human body, it seems desirable to view the type of modern man from a somewhat different standpoint.