Genus: Body blunt at rear; kineties spiralled when body contracts (Illustrated Guide, 1985).@
Species: 500-600 μm long;
with slender, tapered "tail" (How to know the protozoa, 1979).
500-800 μm long;
macronucleus moniliform (Kudo, 1966).
Spirostomum minus Roux,
cell body 800 μm long, 24 μm wide,
peristome 272 μm long (1/3 of the body length),
x 100, Japan, November 1998, by Y. Tsukii
200 μm
400 μm
600 μm; x 100