Phylum Ciliophora - Protozoan
Simple cilia or compound ciliary organelles typical in at least one stage of life cycle; subpellicular cilia present even if surface cilia are absent; two types of nuclei, with rare exceptions; binary fission transverse but multiple fission and budding also occur; sexuality involving conjugation, autogamy and cytogamy; nutrition heterotrophic; contractile vacuole typically present; most species free living but many commensal, some truly parasitic.
This is a very large group divided by the society of Proto zoologists into three classes and numerous orders and suborders. The classes are separated on the basis of characteristics of the ciliary pattern especially around the cytostome.
Examples Paramecium, Didinium, Colpoda, Balantidium, Srenror, Epidinium, Vorticella, trichodina, Ephelota, Tetrahymena.