The history of science is mostly written retrospec tively, a generation or two after the actual events being discussed. Science historians are now analyzing and evaluating the origins of evolutionary and genetical theory in the nineteenth century and a sort of "Darwin industry" seems to have grown up. A history of mammalian cytogenetics by one of the main participants is, hence, a very welcome change, since it has a vividness, an immediacy and a personal flavor which these scholarly tomes and the official biog raphies of scientists mostly lack. The life of the author, Chinese-born, T. C. Hsu, has been a romantic and color ful one, and he is himself a unique personality, so that his book is a very unusual blend of reminiscences, history of his special field (which has transformed human genetics) and wise comments on the mistakes made along the way. The best qualities of a very fine Chinese mind have contributed to Dr. Hsu's career, including this book. Those qualities (which seem to me especially Chinese) include a kind of transparent honesty, a very direct em pirical approach to problems and superb technical ability.