(sten-torr) is a genus of large, trumpet-shaped ciliates, commonly found in freshwater ponds, usually attached with the posterior end to vegetation or other surfaces. Detached individuals may swim freely and adopt an oval to pyriform shape. At the anterior end of the cells a conspicuous peristomial field with a system of adoral membranelles spiralling clockwise to the cytostome. The cilia of the membranelles are much longer than the somatic cilia. The macronuclei of Stentor
may be spherical, elongate to a long strand or formed like a string of pearls. There is a single contractile vacuole with two collecting canals near the cytostome. Some species build transparent loricas of secreted mucus. The cells can be intensive coloured by pigmentation granules located in the pellicula (green, pink, blue, orange or violet). This group of Stentor coeruleus
was collected in freshwater ponds near Konstanz, Germany. This species is couloured blueish and the macronucleus is like a string of pearls.