Paramecium are a single-celled, kidney shaped micro-organisms, or protists, that live in fresh water sources. When studied under the microscope, it is apparent that these Protozoans have everything they need to sustain life contained within this one cell which differentiates them from most other lifeforms which are made up of many cells. The pellicles, cell membranes, of paramecium are surrounded on the outside by cilia or thin hair-like structures that bend in order to propel the organisms back and forth through the water. Cytoplasm is held within the cell membrane. In spite of being a one celled organisms, paramecium have a distinct digestive and excretory system. They also have a system for taking in water through osmosis and releasing it through contractile vacuoles which are placed at each end of the cell.