Abstract
Tne observation on the reproduction of Mytilus grayanus Dunker in this report was carried out at Oshoro. The spermatozoa develop three months earlier than eggs. Consequently, the male individuals are already recognizable by a orange-yellow colour of their mantle in late December, while the mantle of female turns orange-red in the beginning of April in the next year. The spawning begins in the beginning of July and the maximum appears during the latter part of July and August. However, a ?? remarkable number of eggs remains in the ovarian lobules, and they lose the affinity with dyes and the fleshiness gradually, and they degenerate finally at the end of November. By this time the germinal epithelium of ovary becomes active. The germinal epithelium of spermatic lobules rests until the end of October, and then it assumes the active feature.
