This primitive form undergoes numerous changes, to trace and illustrate which, has been the special task assumed by the many recent writers on mythology. In some instances these changes are owing to the blending of the myth with traditions of facts, forming a quasi-historical narrative, the _saga;_ in others, elaborated by a poetic fancy and enriched by the imagination, it becomes a fairy tale, the _märchen_. Again, the myth being a product of creative thought, existing in words only, as language changes, it alters through forgetfulness of the earlier meanings of words, through similarities in sounds deceiving the ear, or through a confusion of the literal with the metaphorical signification of the same word. The character of languages also favors or retards such changes, pliable and easily modified ones, such as those of the American Indians, and in a less degree those of the Aryan nations, favoring a developed mythology, while rigid and monosyllabic ones, as the Chinese and Semitic types, offer fewer facilities to such variations. Furthermore, tribal or national history, the peculiar difficulties which retard the growth of a community, and the geographical and climatic character of its surroundings, give prominence to certain features in its mythology, and to the absence of others. Myths originally diverse are blended, either unconsciously, as that of the Roman Saturn with the Greek Cronus; or consciously, as when the medieval missionaries transferred the deeds of the German gods to Christian saints. Lastly, the prevailing temperament of a nation, its psychology, gives a strong color to its mythical conceptions, and imprints upon them the national peculiarities. The judicious student of mythology must carefully weigh all these formative agents, and assign each its value. They are all present in every mythology, but in varying force. His object is accomplished when he can point out the causal relation between the various features of a myth and these governing agencies. Such is the science of mythology. The philosophy of mythology undertakes to set forth the unities of form which exist in various myths, and putting aside whatever of this uniformity is explainable historically, proposes to illustrate from what remains the intellectual need myths were unconsciously framed to gratify, to measure their success in this attempt, and if they have not been wholly successful, to point out why and in what respect they have failed. In a study preliminary to the present one, I have attempted to apply the rules of mythological science to the limited area of the native American race; in the present chapter I shall deal mainly with the philosophy of mythology. The objection may be urged at starting that there is no such unity of form in myths as the philosophy of mythology assumes; that if it appears, it is always explainable historically.