Each segment is surrounded by one set of muscles, and connected to adjoining segments by a different set of muscles. The alternating action of these two sets of muscles allows worms to lengthen, contract, move, and twist through the soil. Each segment on a worm's body is rimmed with tiny bristles, called setae . By looking closely, you can tell the front, or anterior , of a worm from the back, or posterior . The narrow, slightly pointed end is the anterior, which thickens to force soil apart.
Earthworms have mouths but no teeth.
Everything they eat is pushed through their digestive tracts, where it is ground and worked by muscle action, tiny stones, digestive juices, and bacteria. Earthworms don't have eyes, but they move away from light, especially when it is shined on their front end. Avoiding light, and Earth's surface during daylight, protects worms from predators and from drying out in the sun. Earthworms can be found above ground primarily at night. Worms have special glands to maintain the skin moisture they need in order to take oxygen through their skin and into their blood vessels.