The external surface of the earthworm (Lumbricus) includes a band called the clitellum; which assists in the reproductive process by secreting mucus to provide protection for sperm and eggs. Earthworms contain both sexes (are monoecious or hermaphroditic). Copulation usually occurs at night during warm, moist weather. As the eggs and sperm are released, the mucus from the clitellum creates a cocoon in which fertilization occurs.
The position of the clitellum can be used to determine two things: (1) the location of the mouth and anus and (2) whether the worm is positioned on its dorsal or ventral side. The clitellum is always nearer the mouth than the anus, so therefore by looking at the clitellum you can tell "which end it up"! Also, the clitellum is solid across the dorsal side of the body, but is lighter in color and often indented on the ventral side of the body.
There are two rows of chitinous_bristles (setae) on the ventral surface of the earthworm. These bristles help anchor the worm as it moves through soil.
The body wall of the earthworm (Lumbricus) has strong circular and longitudinal muscles that assist in the movement of the animal through soil. Annelids have a true coelom cavity, which is fluid-filled. When the muscles contract, their pressure on the coelomic_fluid assists the process of locomotion.
Food enters the mouth, passes through the esophagus, enters the crop, then moves into the gizzard. The crop stores food, and the gizzard grinds food. Once food leaves the gizzard, it enters the intestine and heads towards the anus. The intestine runs from (approximately) the clitellum to the anus.
Earthworms have a closed_circulatory_system, which includes five aortic_arches as well as dorsal and ventral_vessels.
Wastes that accumulate in the coelomic fluid and the blood vessels are excreted by nephridia. Nephridia are the worm equivalent of our kidneys.