1. Chromatium okenii(Ehrenberg 1838) Perty 1852, 174AL(Monas okeni Ehrenberg 1838, 15.) o.ken'i.i. M.L. gen. n. okenii of Oken, named for L. Oken, a German naturalist. Cells straight or slightly curved rods, 4.5-6.0 x 8-16 um, occasionally longer, motile by a polar tuft of flagella which is 1.5-2 times the cell length and visible by brightfield(Fig. BXII.Y.5) or phase-contrast microscopy.