I find Carchesium polypinum mainly in old samples from the Simmelried. The colonies of this pertrich ciliate are easy to recognize by the tree-like structure and the non-branched stalk. Carchesium polypinum can be easily distinguished from other colony-forming peritriche ciliates, whose peduncles also contract helically, by the interrupted myonemes at the branching points (s. figs. 3, 4 and 5). This interruption of myonemes causes zooids and also individual branches of colonies to contract independently. In the similar genus Zoothamnium, the myonemes are not interrupted, causing the entire colony to always contract synchronously. A distinguishing feature from Vorticella species is the stalk thickness. In Vorticella, the stalk is always < 10 µm thick, whereas in Carchesium polypinum it is thicker than 10 µm (s. fig. 6). Comparable Epistylis species (e.g. Epistylis procumbens) do not have a central myoneme in the stalk and therefore cannot contract.