In connection with the finding of a Cyclonexis near Eindhoven, a survey is given of the literature about the species of this genus. Cyclonexis annularis is an inhabitant of Sphagnum-pools in the U.S.A. Each cell has two chromatophores. The European Cyclonexis erinus Jane lives in cold and somewhat acid water. In this species each cell has only one chromatophore. A third species has been found in the Urals.