Joseph Needham (1900-95) was a British biochemist and historian, known for his contributions to scientific research and writings on the history of science in China. First published in 1931, this book forms part of Needham's mammoth three-volume work on the subject of physico-chemical embryology. Broadly speaking, the volumes found their basis in three tasks: the collection from various scientific papers of the facts known about the physico-chemical basis of embryonic development; the relation of these facts to each other and to the facts derived from the labours of investigators in morphological embryology; and, on the basis of the first two tasks, ascertaining whether any generally valid principles were apparent. Illustrative figures and tables are included throughout. This book will be of value to anyone with an interest in the works of Needham and the development of chemical embryology.