?Electron-Microscopic Study on Spermatogenesis

Electron microscopic observation was carried out on the structure of sperma-tozoa and sparmatogenesis of black sailfin molley—Mollienesia latipinna which is a fresh-water teleost fish and is generally called " tropical fish " in Japan. Since this fish is in mating period throughout the year and spermatogenesis is done continuously, the spermatozoa at all stages of progress are contained in the testis. The process of the spermatogenesis of this fish is almost the same as that of Sebastiscus marmoratus which is a marine teleost. But it is the remarkable characteristic that in this species the many sperms in a cyst form a perfect sperm-ball in the seminiferous tubule at the last stage of spermatogenesis. The spermatogenesis of this fish is classified into two periods, multiplying period and developing period. In the multiplying period, the nucleolus in the nucleus is clear-but the chromosome is not clear. At the first stage of the developing period, the golgi complex and central body are found in the plotoplasm. The central body appearing at a distance from the nucleus is a short hollow tube surrounded by nine slender tubules each consisting of three fine tubules. The tail flagella appear