OBSERVATIONS ON THE SYMBIOSIS OF PERIDINIUM BALTICUM AND ITS INTRACELLULAR ALGA. I. ULTRASTRUCTURE1,2

Abstract
SUMMARY: The ultrastructure of Peridinium balticum indicates that an eudosymbiont is present within the dinoflagellate. The structure and probable function of the organelles of both protists arc described and discussed. The origin of photosynthetic dinoflagellates from heterotrophic forms by means of a chrysophyte‐like endosymbiont is postulated.