n. pl. - An extensive artificial division of the animal kingdom,
including the parasitic worms, or helminths, together with the
nemerteans, annelids, and allied groups. By some writers the
branchiopods, the bryzoans, and the tunicates are also included. The
name was used in a still wider sense by Linnaeus and his followers.
n. pl. - A more restricted group, comprising only the helminths
and closely allied orders.