Experience has confirmed the author in his earlier opinion that the facts-of embryology are barren and meaningless until they are interpreted in_the light of our knowledge of the evolution of the human body a knowledge which must be -founded on a comprehensive survey Of comparative anatomy and physiology. Hence in this new edition the author has sought to give, not only a descriptive history of the develop ment of the various Systems of the body, but to make the facts intelligible by bringing a knowledge of. Comparative anatomy and evolution to bear on them. Human Embryology and Comparative Anatomy have become vast fields of knowledge. Here they are dealt with only in so far as they bear directly on the nature of the human body, and reflect what the author has found to be useful in the course of his daily work and teaching. Every effort has been made to make the book representative of the latest British Research. In the preparation of the present edition the author has become indebted to a very wide circle of friends too numerous to be mentioned individually. He cannot, however, allow the occasion to pass without a warm acknow ledgment of his indebtedness to Dr. Alexander Low/, Lecturer on Em bryology in the University of Aberdeen, for the help he has given.