Description of Paramecium bursaria:
Cell foot-shaped rather than elongate, the anterior is transversely truncated, the posterior rounded. Attains 80-150 microns long. The oral groove is very wide for most of its length. This species is easily recognised by the presence of green zoochlorellae in the cytoplasm. There are two contractile vacuoles with radiating collecting canals. There is a single, ovoid macronucleus and one elliptical micronucleus.