Paramecium have tiny hair-like structures, called cilia, around the outer edge of their cell that move back and forth in a whip-like fashion, allowing movement in water. Paramecium normally attach to the bottom of a body of water, such as a pond, stream or puddle.
Although paramecium are protists, or single-cell organisms, they are eaten by other protists. Larger organisms, like water fleas and mussels, also eat paramecium. These single-cell organisms reproduce by splitting in half and becoming two paramecium. This process is called binary fission. The inside of a paramecium is filled with a thick gel-like substance called "protoplasm," in which bits of nutrients float.