A subphylum of protozoa in which cilia are present during at least one stage of the life cycle and in which two different types of nucleus (macronucleus and micronucleus) are normally present. Cells reproduce by binary fission. Sexual processes occur. Most species are free-living, although some are parasitic. There is one class, Ciliatea, containing four subclasses, many orders, and numerous genera.
Subjects: Zoology and Animal Sciences — Ecology and Conservation.