In this paper the chromosomes of six freshwater gastropods were reported The names and their chromosome numbers are as follows : [table] Note : s... spermatogonia, m... somatic mitosis, I, II... first and second spermatocytes.

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The oxygen consumption of some freshwater molluscs in Lake Biwa-ko, Hyriopsis schlegelii, Cristaria plicata, Corbicula sandai, Unio biwae and Heterogen longispira, was studied in relation to varying the water temperature and the shell length of animals (Tables 1∿6). The observed respiration is a basal metabolism, not an active one. The oxygen consumption of all molluscs examined decreased according to the shell length increased. The daily periodicity of oxygen consumption of molluscs was observed. In the case of Hyriopsis schlegelii a slight increase of oxygen consumption has been found in 19∿3 o'clock. In Corbicula sandai and Unio biwae, the oxygen consumption increased in 24∿6 o'clock. The oxygen consumption of Heterogen longispira increased at sunrise and sunset, and decreased at midnight and daytime.

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