The adaptations the earthworm has made to its underground life include lacking eyes and ears that can be clogged with soil. It also has a long, tube-like, segmented body which helps it push through the soil.
The segments themselves, save the one near the mouth and anus, have tiny hairs that help to steady the animal as it moves. The earthworm moves by expansion and contraction.
The skin has pores that exude a fluid that keeps the earthworm's skin moist and protects it from the sharp edges of gravel or sand. The fluid also allows the worm to move easily through the soil by lubricating the tunnels that the worm itself digs. The earthworm also injects air into the tunnels as it progresses.
When the earthworm rests, its mouth is protected by a flap of skin called the prostomium. In some kinds of earthworm, this appendage can be flexible enough to grab leaves and blades of grass. The prostomium also serves as a sensory organ for the blind earthworm.
The earthworm lacks lungs and breathes through its skin. Oxygen enters the capillaries and is transported to the tissues in the body. The same thing happens with water and minerals. Many earthworms can also regenerate parts of their bodies if they've been damaged.