INFUSORIA, a name for the group of single-celled animals (Protozoa) usually called Ciliata, and distinguished by numerous, hair-like, protoplasmic processes (so-called cilia), which are used in locomotion and function like oars. The Infusoria are also pecu liar in having two different kinds of nuclei (micronuclei and micronuclei), and a peculiar modification of the process of conju gation. (See PROTOZOA.)