PERIDINIUM BALTICUM (LEVANDER) LEMMERMANN,AN UNUSUAL DINOFLAGELLATE WITH A MESOCARYOTIC AND AN EUCARYOTIC NUCLEUS123

Light and electron microscopy indicate that Peridinium balticum possesses 2 Feulgen-positive, membrane-bound nuclei which divide synchronously. One nucleus has the typical structure of dinocaryotic dinoflagellates, while the other nucleus has a structure typical of eucaryotic organisms. Connections between each nucleus and the endoplasmic reticulum are common. Membrane-bound vesicles are intimately associated with the nuclear envelope of the eucaryotic nucleus.