Background Information
- The planarian is a common flatworm found in fresh water and damp soil. Planarians belong to the order Tricladida of the class Turbellaria in the flatworm phylum, Platyhelminthes.
- There are not any permanent cells in the head of a planarian. If the head of a planarian is cut off it will grow a new head and the old head will grow a new body. That is called regeneration. So if the head and tail of a planarian are cut in half, soon it will have two heads and two tails! Above the head are two organs called eyespots. It's eyes are not like true image giving eyes, the can only sense light. Its head is a triangular shape.
- The planarian's soft, thin body is about ten to thirteen millimeters long.
- Scientists can teach planarians to do simple things, like to find water in a maze. When a trained one gets cut in half, the regenerated planarians learn more quickly than untrained ones.