ANIMAL, AQUATIC, CILIATE, CILIOPHORA, CONTRAST, DIC, DIFFERENTIAL, IMAGED, INTERFERENCE, LIGHT, LM, MICROBE, MICROBIOLOGY, MICROGRAPH, MICROORGANISM, MICROSCOPIC, MICROSCOPY, NOMARSKI, ONE-CELLED, ORGANISM, PARAMECIA, PARAMECIUM, PROTIST, PROTISTA, PROTOZOA, PROTOZOAN, SINGLE-CELLED, SWIMMING, UNICELLULAR, USING, WALKER,