Planarian, << pluh NAIR ee uhn, >> is a type of flatworm. Different kinds of planarians live in streams, lakes, seawater, or damp soil. Most planarians have flat, elongated bodies with a rounded or triangular head and measure 7 to 35 millimeters (about 1/4 to 11/2 inches) long. Some planarians living in soil may grow as long as 35 centimeters (about 1 foot) and may have green, yellow, or black stripes. Most planarians are gray, brown, or black. Many planarians have two dark, cup-shaped eyes. These eyes can detect light and dark, but they cannot form images as the eyes of many other animals do.
Planarians feed on other small animals or on dead animal matter. Grooves or pits on each side of the head can sense food.
Planarians lay fertilized eggs in cocoons. The young worms that hatch look like small adult worms. Many planarians can also reproduce by simply dividing into pieces. Each piece of the worm then can develop into a complete new adult. Planarians have remarkable abilities to regenerate (regrow) any lost or damaged parts of their bodies.
