Genus: Test variable, chitinoid; binucleate (Illustrated Guide, 1985).
Species: Test 30-100 μm in diameter;
height of test about 1/2 the diameter; dome of hemispherical test evenly convex; pseudostome cicular,
central; colorless, yellow, or brown; two vesicular nuclei;
several contractile vacuoles (Kudo, 1966).
Test 100-150 μm in diameter, 50-80 high (Illustrated Guide, 1985).
Arcella vulgaris smaller variety,
test 60 μm in diam., μm high, pseudostome 14 μm in diam.,
P/T=0.23, with three nuclei,
x 640, Kagami-gawa green area, Kochi city, Kochi Pref., Japan, November 2002 by Y. Tsukii
50 μm
100 μm
150 μm; x 400 :
31 μm
63 μm
94 μm; x 640
Arcella sp.,
test 63 μm long, μm wide, pseudostome 17 μm in diam.,
with three nuclei,
x 640, Kagami-gawa green area, Kochi city, Kochi Pref., Japan, November 2002 by Y. Tsukii
50 μm
100 μm
150 μm; x 400 :
31 μm
63 μm
94 μm; x 640