Answer: paramecia

AnswerCrossword Clue
PARAMECIASlide subjects
PARAMECIAMicroscopic denizens of fresh water.
PARAMECIAOne-celled animals.
PARAMECIALittle beasties
parameciaPARAMECIUM, a genus of tiny animals including the slipper animalcule also PARAMAECIUM, PARAMOECIUM