The flatworm’s bilateral body plan has a head with a brain and stereo eyes that enable it to actively hunt. Its mouth and pharynx are in the center of its underside. With no circulatory system, the gut distributes food to all parts of the body.
Flatworm Animation: Body Plan
Next Generation Science Standards for this Video
The body plan of the flatworm is bilateral, with a head that leads—a plan that continues in most animals living today. The structure of this bilateral plan is ideal for an active hunter.
Flatworms are the first animals to transmit signals from sensory receptors along nerve cells to the brain. The head has eyes—the first in the animal world. With this combination, flatworms were the first active hunters.