(coal-ace-ee-um) is a euglenid flagellate in which the cells are attached to the substrate b y means of a mucoid stalk. the euglenids are attached to the stalks by their anterior region. The individual cells may break free from the stalks and swim away, at which time they are indistinguishable from members of the genus Euglena
. Plastids and eyespots can be discerned in some cells. Phase contrast.