A genus of heterotrichous ciliate Infusoria, so named by R. Oken. It possesses a large moniliform meganucleus, accompanied by numerous micronuclei, and has a trumpet shape, when at rest, anchored by pseudopodial outgrowths from the narrow end. It is relatively large, and is much utilized to demonstrate myonemes, and had been also the object of interesting studies on regeneration, any piece, containing with a fragment of the meganucleus at least one micronucleus, regenerating the whole animal (see Regeneration). polymorphus often inhabits a gelatinous sheath and may be green with zoochlorella; it attains a length of 2 1 0 in. S. caeruleus and igneus are coloured blue and scarlet respectively by pigment granules in the ectosarc: E. R. Lankester made a study of the pigment of the former (blue stentorin).