The third issue of this volume is the first to appear in seven years. During this time much has been contributed to the field of sex and reproductive physiology. The author has expertly handled this new material in its relationship with the previously developed knowledge to make a cohesive and homogeneous volume for the benefit of the specialist and student of these subjects. Only an author who has had intimate contact through his own personal researches could manage to prepare an authoritative; readable book without being led astray by the confusing mass of data available in the literature. The author is well qualified to fulfil these reauirements.