Paramecium

Paramecium ( , , plural "paramecia" only when used as a vernacular name) is a genus of eukaryotic, unicellular ciliates, widespread in freshwater, brackish, and marine environments. Paramecia are often abundant in stagnant basins and ponds. Because some species are readily cultivated and easily induced to conjugate and divide, they have been widely used in classrooms and laboratories to study biological processes. Paramecium species are commonly studied as model organisms of the ciliate group and have been characterized as the "white rats" of the phylum Ciliophora.

==Historical background== left|300px|thumb|Paramecia, illustrated by Otto Friedrich Müller|Otto Müller, 1773 right|280px|thumb|Earliest known illustration of Paramecium 280px|right|thumb|"Slipper animalcule," illustrated by Louis Joblot, 1718 Paramecium were among the first ciliates to be observed by microscopists, in the late 17th century. They were most likely known to the Dutch pioneer of protozoology, Antonie van Leeuwenhoek, and were clearly described by his contemporary Christiaan Huygens in a letter from 1678. The earliest known illustration of a Paramecium species was published anonymously in Philosophical Transactions of the Royal Society in 1703.