Two types of spherical forms of this normally flattened organism appear sporadically in our cultures. Hollow spheres have an outer wall of flagellated ventral epithelium. The large fiber cells protrude into the central cavity which can include a closed compartment of flagellated dorsal epithelium. Cells of the outer wall that withdraw their flagellum and leave the epithelium are phagocytozed by fiber cells. Solid spheres consist of an outer layer of dorsal epithelium and densely packed fiber cells in the interior that may also include a closed compartment of ventral epithelium cells. Closely apposed fiber cells may form special cell contacts or pores connecting the cells.