Slipper Animalcule

Slipper-Animalcule or PARAMOECIUM, a genus of Infusoria very abundant in fresh or salt water containing much decomposing vegetable material. The animal is of much value, as the action of the contractile vesicles (q.v.) and the stellate form taken by them during contraction can be easily studied in it. P. aurelia is the commonest species: it is usually a little less than one-hundredth of an inch in length.