Stentor (sten-torr) is a genus of large, trumpet-shaped ciliates, commonly found in freshwater ponds, frequently attached with the posterior end to vegetation or other surfaces. Detached individuals swim freely and adopt an oval to pyriform shape. There is a well-developed peristomial field with a system of adoral membranelles (AZM) at the anterior end, and the AZM spirals clockwise to the cytostome. The cilia of the membranelles are much longer than the somatic cilia. The macronuclei of Stentor may be spherical, elongate, a long thread, or formed like a string of pearls. There is a single contractile vacuole with two collecting canals near the cytostome. Some species of the genus build transparent lorica of secreted mucus. The cells can be intensive coloured by pigmentation granules located in the pellicula (green, pink, blue, orange or violet). Stentor amethystinus can be coloured brownish, violet or purple red. The cell has symbiotic algae. This specimen was collected in freshwater ponds near Konstanz, Germany. Differential interference contrast.