This book, and its companion, "Fish Physiology, Volume 12, Part A", seeks to provide a major synthesis of recent advances, general concepts, and diversity of fish species. It sets out to provide broad coverage of the major aspects of cardiovascular physiology and to act as a major source book for the field. This book discusses the special design of the venous system in aquatic vertebrates, reviews the nature of the secondary circulation in fish, and discusses the probable absence of the lymphatic system. It should be of value to teachers in comparative physiology as well as to the researcher.