hymenostome

hymenostome, any member of the evenly ciliated protozoan order Hymenostomatida. Included in this order are the genus Paramecium, often used in laboratory studies, and the even more widely studied genus Tetrahymena, which can be easily cultured for biochemical and physiological research. The hymenostomes are characterized by a ventral mouth cavity, which is lined by three membranelles of fused cilia on one side and by an undulating membrane on the other side. In the genus Pleuronema...