Compare and contrast the roundworm body structure with those of a flatworm and an

annelid.

A flatworm has a thin, dorsoventrally flattened body ... The gliding locomotion of a flatworm is powered by many tiny cilia on the outer surface of its body. Roundworms, on the other hand, have longitudinal muscles (oriented lengthwise down the worm) that they contract to bend their bodies in a thrashing motion.