aka the Nematoda Class
The nematodes or roundworms comprise the phylum Nematoda. They are a diverse animal phylum inhabiting alot of environments. Nematode species can be difficult to distinguish; and although over 28,000 have been described, of which over 16,000 are parasitic, the total number of nematode species has been estimated to be about 1 million. Unlike cnidarians and flatworms, nematodes have tubular digestive systems with openings at both ends.