∞ generated and posted on 2016.09.03 ∞
Members of animal phylum Nematoda.
Roundworms are more or less round in cross section. They lack, however, the segments of the more familiar segmented worms such as one sees in earthworms. Members of phylum Nematoda are referred to as nematodes and include a vast number of individuals, most of which are free living but some of which instead are parasitic.
Parasitic roundworms include pinworms, hookworms, heartworms, and the familiar (to the laboratory) Ascaris. The important laboratory model animal, Caenorhabditis elegans, a.k.a., C. elegans, is a roundworm.
Note that nematodes actually are described as pseudocoelomates rather than strictly coelomates since their "coeloms" technically are not contained within mesodermal tissue.