closely correlated with environment, yet shows a tendency to conform to it. This would be consistent with our conclusion that the population of a center was relatively stable, so that an occasional immigrant group could be gradually leveled by intermarriage. But the immigrant group need not change its language so long as it maintains its social independence, nor does the environment appear to put any pressure upon its members to so change it. What uniformity of somatic type we then have is merely the accidental result of sexual contact, while the lack of linguistic uniformity is due to the former history of the group. It follows then that about all that survives in an immigrant group is its speech, for both its culture and blood gradually disappear in the new environment. But blood being a biological character, in contrast to culture, it is subject to certain very definite laws of inheritance and the particular forms the mixture will take are likely to be various. Culture on the other hand, can be entirely displaced even within a single generation.
Finally, with a few generalizations we may summarize this long and tedious, but we trust not unprofitable, survey of aboriginal man and his varied characters. It appears a fair assumption that so long as the main sustaining habit-complexes of life remain the same in an area, there will be little change in material culture. This may be in part an explanation for the lack of close correspondence between the historic cultures and archæology in the several parts of the great maize areas in contrast to identity elsewhere. The bison, salmon, wild acorn, and guanaco must have been in their respective habitats for a long, long time, and a culture once developed around them could be displaced only by a radical change, such as the introduction of agriculture or pastoral arts. Now the regions where maize was found in use at the opening of the historic period are just those in which archæology shows the most disparity. It seems then, that the environment as a static factor conserves the types of culture and because of this weighting of one of our three great groups of characters, breaks their unity, so that the same
