A Histological Study O F T H E Testes of T H E Sockeye Salmon (oncorhynchus Nerka)

Most of the earlier investigations on the gonads of teleosts have been concerned with the lineage of germ-cells (Nussbaum, 1880; Eigenmann, 1891; Dodds, '10; Sink, '12; and Bachmann, '14). The structural development of the radialtype testis, as well as the history of the germ-cells in Cottus, was described by Hann ( '27). Essenberg ( '23) traced the development of the acinus-type testis in Xiphophorus. The structure of the mature testes has been described for Perca (Turner, '19), Gambusia (Geiser, '21)' Gasterosteus (CraigBennett, '30), Fundulus (Matthews, '38), Phoxinus (Bullough, '39), and Galeichthys (Frederick, '41). These papers deal also with the reproductive cycle. This study was undertaken to trace any correlations which might exist between the life history of the Pacific salmon, particularly of a certain landlocked type, and the histology of their testes. On reaching sexual maturity, the males of the Pacific salmon (the genus Oncorhynchus) exhibit an extreme development of the secondary sexual characters. A pronounced hump appears on their backs, their jaws become elongated and distorted, and the skin becomes thickened, so that the scales are deeply embedded.2 The males as well as the females die soon after their single spawning season.