Phagotrophic Ingestion of a Blue‐Green Alga by <i>Ochromonas</i>*†

SYNOPSIS Anacystis nidulans disappeared rapidly from culture in the presence of an unidentified species of Ochromonas. Disappearance was light‐independent and could be induced neither by bacteria associated with, nor by soluble products released from the flagellate. Electronmicrographs of mixed cultures revealed numerous A. nidulans cells in various stages of digestion within vacuoles of Ochromonas. Evidently the disappearance of the alga from culture resulted from phagotrophy by the chrysomonad. A 2‐stage digestive process is suggested whereby A. nidulans cells are initially sequestered in the posterior “leucosin” vacuole and then undergo the terminal stages of digestion and elimination in smaller, peripheral vacuoles.