This amoeba (syn. Jodamoeba buetschlii, J. williamsi) lives as commensal in the human intestine and has in its cyst stage (6–15 μm) a very large vacuole-containing glycogen. The single nucleus contains a large nucleolus, but has no peripheral densification. The amoeboid stage, which measures 10-20 μm, may form two pseudopodia at the same time. This species was described by von Prowazek in the year 1912 and occurs mainly in the colon of monkeys, pigs and rats.