抄録
A number of the top-shell were put in a bamboo basket and kept folating in a littoral pond (Fig.1) excavated in the rock. They were exclusively fed on the alga, Eisenia bicyclis, and found growing slower (Fig. 2, solid circles) than those living outside the pond (same, squares). Remarkably enough, the spines on the shell were suppressed in growth when transferred into the pond (Fig. 3). The observations on the water-samples taken inside and outside the pond (Table 4) and an analysis of the already published data by previous writers (Table 5) showed that inferiority of the water especially in specific gravity, alkaline reserve, contents of Cl and K was mostly responsible for the changes.
