Some Histological Notes on the Gonads of Tapes japonica DESHAYES

1. Histological studies on the gonads of the clam, Tapes japonica DESHAYES, in Sasebo Bay have shown that the reproductive follicles of all individuals contract and become inactive both in summer and winter, and this clam spawns twice a year in spring and autumn (Table 1). 2. In November, some individuals about 12mm. in shell length have mature gonads, and many individuals about 15mm. in shell length spawn (Table 2, Plate Figs. 1-3). 3. Comparison of maturity of the gonads has been made in normal clams and in clams cultured in a wire cage hanging in the sea. The results show that the hanging culture method has great effect on gonad development in these clams. In cultured clams, the gonads mature in July. while in normal individuals the gonads mature in late August or September (Table 3, Plate Figs. 4-10).