Carchesium (ciliate)

Carchesium is a genus of usually colonial peritrich ciliates in the Vorticellidae with a spirally contractile stalk. The inverted bell-shaped cells have an oral lip as in Epistylis.

The genus has a cosmopolitan diribution in freshwater and is a common part of the fauna of the aerobic stages of waste water treatment plants, such as activated sludge and trickling filters.