Roundworm

Roundworm, or nematode, any of more than 10,000 species of worms making up the phylum Nematoda, found in terrestrial, freshwater, and marine forms. All roundworms are long and thin, tapering at each end, and are covered with a complex cuticle. The internal organs are suspended within a fluid-filled cavity pseudocoeom. The free-living and plant-parasitic forms are usually microscopic, but animal-parasitic species may reach up to 3.5 ft (1.07 m). Rotifers, and horsehair worms are in the same phylum.