Pseudopodia as semi-eruptive anterior bulges with clear hyaline caps. Endoplasm granular with vesicles but without crystals or contractile vacuole. Nucleus ring-like, with peripheral granules and a central endosome. Cysts round and smooth. Mature cysts of some species multinucleate. Many varieties reported. Habitat: parasite of the intestinal mucosa of man, apes, monkeys, dogs, cats, pigs, rats, cattle and other animals; some species commensal in mouth; can migrate to other tissues via the bloodstream; causes mild to severe diarrhoea on occasion lethal. Type species: Entamoeba coli Cassigrandi & Barbagallo, 1895.