There is hardly any subject, except of course psychology, so beset with prejudice, bias and superstition as the study of heredity. It is therefore an agreeable surprise to come across a book such as this is, one written with complete objectivity and profound knowledge. Professor Hogben is one of the three or four biologists in the world who are equipped, both biologically and mathematically, to make important contributions to this subject and to assess our present state of knowledge on it. There being no reference to psycho-analysis in the book, this is not the place to discuss its contents, but every analyst would do well to inform himself of the present state of scientific knowledge in respect of the problems that concern him, e.g. consanguinity, inbreeding, inheritance of mental disorder and defects, etc. For those who are averse to reading a highly technical treatise, in which mathematics play an essential part, the reader may be referred to a more general exposition of the subject which Professor Hogben has written as a chapter in another book called Science To-day.