REPRODUCTIVE BIOLOGY AND PHYLOGENY OF FISHES - PHYLOGENY REPRODUCTIVE SYSTEM VIVIPARITY SPERMATOZOA

The animals loosely termed fish constitute more than half of all known vertebrate species. There are approximaately 27,000 described living species of boney fishes, about 70 species of hagfishes and some 34 species of lampreys. Approximately 970 species are chrondrichthyans, the sharks and their relatives, which were the subject of volume 3 in this series. It is perhaps because fishes live in a buoyant medium, whether it be fresh or sea water, that they show a diversity in body shapes that is unparalleled by other vertebrates. There is also a unique diversity in the modes of reproduction, whether by external or internal fertilization, and this, with the morphology and fine structure of the reproductive system and its components, is the subject of the present volume. A large part of this book deals with the ultrastructure of spermatozoa, with some discussion of phylogenetic implications.