Abstract
In this article the author deals with the vital force and the dryness of a Japanese common oyster drill, Purpura clavigera (KÜSTER), in the air, under different degrees of temperature given below, and some discussions of these items may be given. The dryness is expressed as W0-Wu/W0×100, where W0 is initial total weight of the oyster drill; Wu, total weight of the animal in question at time n. The duration of life of the oyster drill in the air under different average temperatures, such as -4.4°C., 6.8°C., 13.1°C., and 30.7°C., is 124.8, 223.2, 165.6, and 79.2 hours respectively on average (Table 2 and Fig. 1). These durations are not longer than those taken by HORI13) on the Japanese oyster, Osirea gigas, about 3.6×2.7cm. in size. Accordingly it may be said that the method exposing oyster clusters to the air is available for extermination of the oyster drill living on them. In this connection it shoud be mentioned herewith that the lethal dryness for the oyster drill is of ca. 10% in the cases of the air temperatures higher than 6.8°C.
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