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.
På grund af de mange forskere der frekventerede hans butik blev hans egen interesse for zoologien forøget, og det lykkedes ham endda at blive en international autoritet indenfor bløddyr og tropiske muslinger med speciale i venstresnoede snegle.