Paramecium protozoa. Light micrograph of Paramecium caudatum., a single-celled creature (protozoan). The internal structures (organelles) can be seen. P. caudatum lives in stagnant water and feeds on bacteria and plant particles. It propels itself through the water by beating the tiny, hair-like structures (cilia) on its surface. Magnification: x133 at 35mm size.