The author presented this material as a course of lectures at Princeton. The introductory four or five chapters are easy, popular reading, and no doubt they cover the points made in books on biology or anatomy, that is, they explain how one-called animals and plants reproduce themselves. The reminder of the book is pretty technical, when he starts in on the various hormones and what part they play in the process of reproduction. He traces, step-by-step, the various stages of pregnancy, both in animals and in humans, how the various hormones function at given times and so on. No doubt it is a sound work and should be of interest and help to medical students, nurses, doctors. But it does not seem to us to be popular enough in presentation to appeal to the layman.