[ref. ID; 2014]
Inverted bell-shaped zooid borne upon a stalk which contracts in a zigzag manner. The organism solitary, never colonial and carried on an unbranched stalk, circular in cross-section. The myoneme travels down the inside of the stalk parallel to its walls. Haplocaulus is most easily confused with two other solitary peritrich genera whose stalks contracts spirally, these are Vorticella and Pseudovorticella.
Quote; Colin R. Curds, Michael A. Gates and David McL. Roberts "British and other freshwater ciliated protozoa Part II Ciliophora: Oligohymenophora and Polyhymenophora" Cambridge University Press, 1983 (ref. ID; 2014)