Order: Unicellular or Colonical.
Family: Unicellar; cylindroid; spiny protrusion at one end.
Genus: Chloroplasts absent (Illustrations of The Japanese Fresh-water Algae, 1977).
Harpochytrium atkinsonianum ?,
cell body cylindroid, slightly curved, 110 μm long, 4.5 μm wide,
tapered at both end, no chloroplasts,
x 400, x 640, Japan 199? by Y. Tsukii
50 μm 100 μm 150 μm; x 400 : 31 μm 63 μm 94 μm; x 640
Harpochytrium atkinsonianum Pascher: Cell body cylindroid, slightly curved; tapered at both end; attached to other algae (e.g., Zygnema, Oedogonium) at one end; no chloroplasts; many oil drops; 70-120 μm long, 5-6 μm wide (Illustrations of The Japanese Fresh-water Algae, 1977).