Their tissues are organized. 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.