List of animal phyla
Nematoda: the round worms. For purists, the name Nemata has priority. Despite their rather limited body form, this is a major phylum, with huge numbers in every conceivable habitat. "More than 15,000 species have been described, of an estimated one million living species".p90 Nematodes include both free-living and parasitic species of plants and animals, including man. Of their large number of species most are likely to be parasites. Nematodes are one of the few life-forms in which each species has a defined number of cells.