Phylum nematoda consists of animals going by the common name of roundworms. They are triploblastic protostomes exhibiting bilateral symmetry and possessing a pseudocoelom. Roundworms are ectysozoans, indicating that they moult/shed their exoskeleton periodically as they grow. A hydrostatic skeleton allows them to move by thrashing about, as can be observed in many THRILLING Youtube videos. In addition, they are virtually ubiquitous, found in nearly all marine, freshwater, and terrestrial environments, and are usually parasitic. I'm a biology major, and this is the first time I've ever had any practical application of this knowledge whatsoever.