This little paperback book includes a series of lectures given in memory of Karl Taylor Compton, ninth president of the Massachusetts Institute of Technology. Doctor Lwoff is head of the department of microbial physiology at the Institut Pasteur in Paris. In his lectures he attempts to give a concise explanation of the biological order as a whole. The book is well written and may be regarded as a sophisticated summary of the nature of life. It is especially directed towards young physicists and chemists but should be of value to students of the biological sciences as well.