|The earthworm absorbs oxygen and gives off carbon dioxide through a thin skin. This skin is protected by a thin cuticle secreted by the epidermis and kept moist by a slimy mucus also produced by epidermal cells. A moist surface is necessary for oxygen to be absorbed and carbon dioxide to be given off. If the worm is dried by the sun, it will die because the exchange of gases can no longer take place.
Nitrogen-containing waste materials from cell activities are removed to the outside of the body by little tubes. There are two such structures, called nephridia, in each segment except the first three and the last.