Stories We Like: A Guide to the Comma
any dorsoventrally flattened, oval protozoan of the ciliate order Hypotrichida, very widely distributed in both fresh and salt water. Instead of having simple cilia (hairlike processes), the hypotrichs have groups of fused cilia (cirri) arranged on the ventral surface and used for crawling. The dorsal surface is frequently equipped with rows of short, presumably tactile, bristles. Hypotrichs reproduce by sexual conjugation (nuclear exchange) and by asexual binary division. In numerous cases, they encyst. Representative hypotrich genera include the ellipsoid Oxytricha, the freshwater Gonostomum, the sometimes violet or rose-coloured Uroleptus, and, best known of all, Euplotes.