The development of the diatomChaetoceros salsugineus from Amurskii Bay in the Sea of Japan was investigated in laboratory culture. It is shown that the intraspecific taxaC. salsugineus f.salsugineus, C. salsugineus f.curtus, andC. salsugineus f.solitarius correspond to particular stages in the development of this species in culture. Problems of the taxonomy and biology of this species are discussed. It is assumed that the life cycle ofC. salsugineus includes a benthic stage represented by resting cells.