They have eyspots that make them appear crosseyed. Planaria are freshwater predators and scavengers. Flukes are parasitic. Tapeworms are also parasitic and are adapted for life within a host. They have hooks that enable to attach to tissue, and they absorb the necessary nutrients through their body.
Roundworms have a body cavity that houses the organs and serves as a circulatory system.
They have both a mouth and an anus. Trichinella, pinworms, hookworms, brainworms, and filarial worms are included in this phylum. Brainworms wiggle into a snail, which is eaten by a deer. They travel through the stomach, into the nerves, up the spinal cord, and into the brain where they lay their eggs. The eggs hatch and migrate to the lungs.