Paramecium bursaria protozoan. Polarised light micrograph of two paramecium bursaria. This species of protozoan inhabits freshwater, where it feeds mainly on bacteria. It moves by beating its cilia, hair-like extensions that cover its body. The small green bodies inside the organism are individual Zoochlorella sp. algae, which have a symbiotic relationship with the protozoan. They photosynthesise inside the Paramecium, providing it with sugars and oxygen, while deriving protection from their host. Magnification: x400 when printed 10 centimetres wide.