an order of protozoans of the subclass Spirotricha of the infusoria. Includes a number of genera, among them Oxytricha, Stylonychia, Euplotes, Aspidisca, and Kerona (a parasite of the hydra).

Hypotricha are characterized by considerable compression of the body and modification of the ciliated covering: on the dorsal side, the cilia are transformed into short, tactile bristles; on the ventral side, they unite to form so-called cirri, which are usually distributed in groups and serve for locomotion over the substrate. Asexual reproduction (binary fission), as well as the sexual process—conjugation—are characteristic of Hypotricha. The majority of species are free-living; they are found in fresh, brackish, and sea waters.