Abstract: In this paper a species of Trichophrya (Suctoria) from the gills of Ctenopharyngodon idellus is described. Owing to the body of adult parasite being rather variable, with short and few tentacles, the pellicle with some regularly arranged basic granules similar to those of the ciliary rows, both young and adult having a short stalk on the posterior end of the body and the anterior end of ciliospore possessing a small cone and seven ciliary rows, the present species is justified to be new to science and named Trichophrya variformis sp. nov.Living organism is soft, flattened and yellowish in colour. The body is variable in form, with cytoplasm flowing toward one direction, or forming pseudopodia at other parts. It is capable of moving slowly. In preserved specimens, the body is rounded, rodlike or ellipsoid, with a bunch of 6—8 tentacles on the anterior end. There is a macronucleus, sausage-like or banana-shaped, and a single micronucleus, rounded, situated near the macronucleus; a single contractile vacuole is also present. Length of adult is 70 (46—96) μ, width is 34 (19.2—42.0) μ, thickness is 11—14 μ and a spherical ciliospore is 30—40 μ in diameter. The young organism has a short stalk and a bunch of tentacles.According to the characteristics of Trichophrya variformis which possesses the ciliary granules, the attaching stalk at posterior end, the ciliospore or the cone and seven ciliary rows in the middle of the body, the author is of the opinion that this species may be a transitional form representing a possible evolutionary course from attaching free living to parasitic living. The presence of the ciliary granules and ciliary band in this species is also important and interesting for tracing the ontogeny and phylogeny of the Suctoria.Fig. 1—15. Trichophrya variformis sp. nov.1. An adult, showing the cytoplasm of anterior part as pseudopodia of amoeba, a short cone at posterior end, and the pellicle with some regularly arranged basic granules and division of macronucleus and micronucleus as well as the ciliary band just being developed. Living organism.2. An adult, showing the amoeba-shaped pseudopodia of the anterior part of the parasite and internal structure of the body. Living organism. 3. An adult, an embryo budding just drilling out from the parental generation and the cytoplasm of young suctorian squeezing to the outside of the body. F. G. A. (Fixed with Formalin and cleared with Glycerine Alcohol)4. An adult, showing six short tentacles at the anterior end of the body, the structure of macro-and micronucleus and their position as well as the indistinet short stalk. F. G. A.5.-6. An adult, showing the outline, stalk and the internal structures of the body. F. G. A.7. A part of tentacles, showing the state of terminal end of tentacle when expanding, Living organism.8. A part of posterior end of an adult, showing the pelIicle with some regularly arranged basic granules of ciliary rows. F. G. A.9. The eary stage of young suctorian, showing its stalk, tentacles, macro-and micronudeus, the position of contractile vacuole and the basic granules on the pellicle, S.H. (Stained with Haematoxylin)10. An adult, showing the tentacles, position of macro-and micronucleus and the indistinct stalk at the posterior end of the parasite, F. G. A.11. An adult, showing the development of an embryo budding. F. G. A.12. A young parasite, showing the anterior end of the parastite with a small perforatorium, ciliary band, macro and micronucleus and the position of the contractile vacuole. S. H.13. A young parasite, Showing seven ciliary rows and many striations of ciliary row on the pellicle of the ciliospore. S. H.14. A young parasite, showing the anterior end of the ciliospore with a small perforatorium, seven ciliary rows and a row without cilia. F. G. A.15. Lateral view of an adult, showing the position of macro-and micronudeus and contractile vacuole. F. G.A.