Some years ago, when fresh from the study of Sir J. G. Frazer’s epoch-making work, _The Golden Bough_, I was struck by the resemblance existing between certain features of the Grail story, and characteristic details of the Nature Cults described. The more closely I analysed the tale, the more striking became the resemblance, and I finally asked myself whether it were not possible that in this mysterious legend—mysterious alike in its character, its sudden appearance, the importance apparently assigned to it, followed by as sudden and complete a disappearance—we might not have the confused record of a ritual, once popular, later surviving under conditions of strict secrecy? This would fully account for the atmosphere of awe and reverence which even under distinctly non-Christian conditions never fails to surround the Grail, It may act simply as a feeding vessel, It is none the less _toute sainte cose;_ and also for the presence in the tale of distinctly popular, and Folk-lore, elements. Such an interpretation would also explain features irreconcilable with orthodox Christianity, which had caused some scholars to postulate a heterodox origin for the legend, and thus explain its curiously complete disappearance as a literary theme. In the first volume of my _Perceval_ studies, published in 1906, I hinted at this possible solution of the problem, a solution worked out more fully in a paper read before the Folk-lore Society in December of the same year, and published in Volume XVIII. of the Journal of the Society. By the time my second volume of studies was ready for publication in 1909, further evidence had come into my hands; I was then certain that I was upon the right path, and I felt justified in laying before the public the outlines of a theory of evolution, alike of the legend, and of the literature, to the main principles of which I adhere to-day.