Some fragments of this book have already appeared in the Modern Language Review, Modern Languages, and the Bulletin of the John Rylands Library. The only abbreviations used in the foot-notes are A.T.F. (Anciens Textes français), M.L.R. (Modern Language Review) and P.M.L.A. (Publications of the Modern Language Society of America). I have to thank Professors R. A. Williams, E. Vinaver, J. Dechamps, Mr H. S. Bennett and Dr L. C. Harmer, who have read the manuscript, for much valuable criticism and advice. But they are in no degree responsible for the opinions which I have attempted to expound.