The Dinoflagellate Transverse Flagellum: Three‐dimensional Reconstructions From Serial Sections1

Serial sections through in situ transverse flagella of the dinoflagellate Peridinium cinctum f. irregulatum (Lindem.) Lefévre are presented. Three‐dimensional reconstructions based upon tangential and radial series show a helically coiled axoneme lying external to and distinct from an accessory strand. Hitherto undescribed vesicles within the expanded flagellar sheath are suggested to provide a decoupling effect between axoneme and strand. The flagellar axis bears two types of hair but anchoring threads between cingulum and flagellum have not been found. Functional and taxonomic implications of these observations are briefly discussed.