See Baker, Employment for the Microscope, ed. 2, 1758.
Saville Kent's valuable Manual of the Infusoria (1880-1882), which gives figures of every genus and descriptions of every species known at that date, includes the Flagellates in its scope.
Orders 1 and 2 constitute together the Holotricha of Stein; Bütschli regards 3 to 6 as sections of Spirotrocha.
Dextrorse in all but Lichnophora and Spirochona.
Each membranella is a transversely elongated oval in reality, and below it is a double row of basal granules, corresponding to the individual cilia that constitute it. Similarly, the undulating membranes have a single row of basal granules.