Paramecium
Pprotozoa are single-celled animals that come in many shapes and sizes. The most common shapes are round, oval, bell-shaped and slipper-shaped.
Paramecium is the slipper-shaped protozoan. Paramecium has a large nucleus called a macronucleus, which is essential for its survival, and one or two small nuclei called micronuclei, which are essential for sexual reproduction.