CHAPTER XIII.

GROWTH AND VARIATION OF FISHES 170

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.