Interphako interference contrast light micrograph of Paramecium caudatum, showing contractile vacuoles (circular with canals). These vacuoles are organelles that remove excess fluid out of the cell. Paramecium caudatum are ciliate protozoa that inhabit freshwater, where they feed mainly on bacteria. These protists have hair like cilia for movement and feeding. Magnification: x363 when printed 10 centimetres wide.