Paramecium bursaria. Light micrograph of the slipper-shaped ciliate, Paramecium bursaria. It is a one-celled protozoan. Many smaller green cells can be seen within the body of this Paramecium. These are cells of a green alga, probably Chlorella, living symbiotically within the organism. These symbiotic algae photosynthesize and provide energy, carbon, nitrogen and oxygen that the animal may use; in return the alga obtains carbon dioxide, ammonia, salts and shelter. Paramecium commonly inhabit both water and soil. They move about by beating fine hairs, called cilia, seen here outside the body. Magnification: x110 at 35mm size.