[in Japanese]

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Two kinds of typical spermatozoa, macro- and micro-typical, were observed in Epitonium (Cinctiscala) eusculptum and E. (C.) eximium. The whole and head lengths of macro-typical spermatozoa were about two and 1.5 times larger than those of micro-typical ones (Tables 1 and 2). Their chemical components were studied by some histochemical methods, but the results showed no qualitative difference between the two kinds. Typical and atypical spermatozoa were observed in the seminal vesicle and sperm duct in a state of "spermatozeugma". Two types of spermatozeugmata were distinguished, i.e. "macro-type" consisting of an atypical spermatozoon attached exclusively by macro-typical spermatozoa, and "micro-type" likewise only by micro-typical ones. They are different also in the shape of atypical spermatozoa and their site of attachment of typical spermatozoa. Micro-type spermatozeugmata were observed more abundantly than macro-type in both species (Table 3). The behaviours of the two types of spermatozeugmata in the sea water were compared. A considerable difference was observed between the two types in the behaviour of typical spermatozoa, i.e. micro-typical spermatozoa became free from atypical spermatozoa more easily than macro-typical ones. Observations on the testis showed that the spermatozeugmata were formed in the lumen of seminiferous tubule after both typical and atypical spermatozoa had been completed.

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Fifty-one molluscan species, including those taken alive and dead, were found out of biological samples dredged off Akkeshi, Hokkaido, by the R/V Tansei-Maru during her KT 68-9 cruise. The dredging was made at five stations with depths ranging from 45m to 135m. The result of identification of the material suggested that there may exist a faunal boundary between 45m-depth and deeper zones. A scarcity of commonness even among the species from four deeper stations, namely, 65m, 85m, 110m and 135m deep may most probably be attributed to variations of such an environment as bottom texture. The molluscan assemblages observed here represent a part of shelf fauna inhabiting under a cold current.

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