 Due to his encountering so many scientists in the bookshop, his interest in zoology was only increased, and he actually succeeded in becoming an international authority in the field of molluscs and tropical mussels, mainly specializing in the left-oriented snails.Due to his expertise, he was assigned to investigate the collection of these snails brought home from the Danish expedition to Siam (1899-1900), and in 1909 his main work appeared