Paramecium protozoa. Light micrograph of a group of Paramecium caudatum, which are single-celled creatures (protozoa). The internal structures (organelles) of the creatures can be seen. P. caudatum lives in stagnant water and feeds on bacteria and plant particles. It propels itself by beating tiny, hair-like structures (cilia) which project from its exterior. Magnification: x 33 at 35mm size.