While the four stages in development of belief are fundamentally distinct, they nevertheless overlap in such manner as apparently, and in a measure really, to coexist and blend. Culture progress is slow. In biotic development the effect of beneficial modification is felt immediately, and the modified organs or organisms are stimulated and strengthened cumulatively, while the unmodified are enfeebled and paralyzed cumulatively through inactivity and quickly pass toward atrophy and extinction. Conversely in demotic development, which is characterized by the persistence of the organisms and by the elimination of the bad and the preservation of the good among qualities only, there is a constant tendency toward retardation of progress; for in savagery and barbarism as in civilization, age commonly produces conservatism, and at the same time brings responsibility for the conduct of old and young, so that modification, howsoever beneficial, is measurably held in check, and so that the progress of each generation buds in the springtime of youth yet is not permitted to fruit until the winter of old age approaches. Accordingly the mean of demotic progress tends to lag far behind its foremost advances, and modes of action and especially of thought change slowly. This is especially true of beliefs, which, during each generation, are largely vestigial. So the stages in the evolution of mythologic philosophy overlap widely; there is probably no tribe now living among whom zootheism has not yet taken root, though hecastotheism has been found dominant among different tribes; there is probably no people in the zootheistic stage who are completely divested of hecastotheistic vestiges; and one of the curious features of even the most advanced psychotheism is the occasional outcropping of features inherited from all of the earlier stages. Yet it is none the less important to discriminate the stages. THE SIOUAN MYTHOLOGY