Respiration, 135—Structure and arrangement of the gills, 136—Pseudobranchiæ, 140—Accessory respiratory organs, 142—Air-bladder; its varieties, structure, and functions, 142.
Fishes are dioecious, 157—Hermaphroditism, 157—Oviparous and viviparous fishes, 157—Generative organs of Branchiostoma, 157—of Cyclostomes; their ova, 158—Female organs of Teleosteans and their ova, 158—Instances of females taking care of their progeny, 160—Male organs of Teleosteans, 162—Instances of males taking care of their progeny, 163—Generative organs of Ganoids, 163—of Chondropterygians and their ova, 166.
Changes of form of the body or certain parts, normally accompanying growth, 170—Changes dependent on sexual development, 176—Secondary sexual differences, 176—Mixogamous, polygamous, and monogamous fishes, 177—Hybridism as a cause of variation, 178—Regular and irregular growth of fishes, 178—Leptocephali not a normal state of development, 179—Changes of colour of the muscles and external parts; chromatophors, 182—Albinism, 183.
