Characterization of Two Sibling Species of the Genus Stylonychia (Ciliata,Hypotricha): S. mytilus Ehrenberg, 1838 and S. lemnae n. sp. I. Morphology and Reproductive Behavior1

All Stylonychia mytilus-like ciliates which were collected and sent to us during the last 20 years belonged either to S. mytilus or to a new species, S. lemnae, which is described here. The only morphological differences are the shape and the size. Stylonychia mytilus that have been starved for one day average 300 μm in length, and S. lemnae starved for a day are 230 μm long. The occurrence of mating types is described.