The purpose of the first four volumes of the Handbook of Genetics is to bring together collections of relatively short, authoritative essays or an- notated compilations of data on topics of significance to geneticists. Many of the essays will deal with various aspects of the biology of certain species or species groups selected because they are favorite subjects for genetic investigation in nature or the laboratory. Often there will be an encyclo- pedic amount of information available on such species, with new papers appearing daily. Most of these will be written for specialists in a jargon...