have con f used biological with cultural phenomena, and the collapse of the classical theory of universal stages in social evolution. Now the most hopeful approach to the concept of cultural change would seem to be to regard the process as selectively accumulative in time, and cyclical or oscillatory in character. This approach leads at once to a somewhat different view of historical continuity and recognizes two aspects of the principle. In the first place the main stream of human culture, which Morgan tried (without success) to prove passed through universal evolutionary stages, is found to be something of an abstraction. Morgan and his school seem to have confused this abstract idea of a main or central stream of human culture with the facts of concrete similarities in different areas at different times. In so far as these concrete similarities exist, it would now appear that they are really examples of similar cyclical changes in independent culture groups and not illustrations of universal cultural stages in one continuous world-wide stream of unified cultural evolution. The critical work of Boas,1 Lowie,2 Goldenweiser,8 Wissler,4 Krodber5 and others, has been of immense value in clearing the ground of obsolete theoretical structures, but on the other hand no constructive theory has been advanced to meet the need of a logical explanation of the larger processes of cultural con? tinuity. Historians, archaeologists, sociologists, economists and anthropologists have all at one time or another mentioned various significant elements of cultural change, but there have been few attempts5* to organize these elements into sets of related hypotheses which might be combined into the preliminary outline of a tentative theoretical explanation. The purpose of this article is to approach this problem. The second form of historical continuity con? sists of separate streams of group cultures. This process is illustrated in the cycles of national growth and decay. For the sake of analysis the phenomena may be split up into cycles of (1) material culture, and of (2) non-material culture. Historians have tended to hold to this idea of separate streams of group (national) culture, and have rightly criticized the main-stream-universalstage-theory. With these two different principles of historical continuity mentioned, let us pass on to a more detailed examination of our problem.