What are the major differences between flatworms (platyhelminths) and roundworms (nematodes)?

What are the major differences between flatworms (platyhelminths) and roundworms
(nematodes)?

The flatworms lack a coelom, while the nematodes possess a pseudocoelom. The flatworms arose much
earlier than the roundworms, and their digestive tube is a two-way conduit, similar to the situation in the
cnidarians. On the other hand the nematodes possess both a mouth and an anus, so that their digestive
tube is a one-way system, with greater specialization of mouth and anal regions possible. Because they
possess a body cavity (the pseudocoel), nematodes are not solid, whereas the flatworms are. Also, the
nematodes have a tough cuticle, which is protective and especially adaptive in parasitic roundworms;
flatworms do not have such a cuticle. Motile flatworms, such as planaria, move largely by beating their
surface cilia. Nematodes move only by a whiplike movement of the whole body produced by the contraction
of longitudinal muscles.
Most nematodes are dioecious (having separate sexes), but the flatworms are usually hermaphroditic.
A greater complexity of the nervous system also characterizes the nematodes