Abstract
Adult males of Hynobius retardatus were collected in the field throughout the year except winter months, and the seasonal changes in the testes, fat bodies and Wolffian ducts were examined anatomically and histologically. Slight spermiation was beginning in some specimens just before entering the breeding pond early in May. In specimens returning to land just after breeding, spermatogonial proliferation was beginning. Spermatozoa appeared in August, and spermatogenesis had been completed in all the seminiferous lobules by September. The testes were smallest in June and largest in August, and the ratio was 1:25 in weight. The most conspicuous development of the Wolffian ducts was seen in the specimens just before entering the pond, and the ducts were most slender late in July.
