Earthworms reproduce through a unique copulation process whereby two worms line up against each other and excrete a type of mucous that forms a layer that encapsulate their bodies. Both worms release sperm into the mucous. After various other processes are completed, the sperm reaches the sperm receptacles on the opposite worm.
Earthworms are hermaphroditic, meaning they have both male and female sex organs. After the worms copulate, they separate. While on their own, a band called the clitellum encircles a small portion in the middle of their bodies and secretes another type of mucous. As the worm moves, the mucous passes over a sac on the worm that holds the eggs. The eggs stick to the mucous, and the worm continues to move. Soon, the mucous and egg mixture passes over the sperm receptacles that are holding the sperm that was provided by the other worm during copulation. The worm then completely removes its body from the mucous and releases the cocoon of fertilized eggs into the soil. The worm embryos develop in the cocoon and are born and fully developed by 60 to 90 days. This process of reproduction takes place every seven to 10 days. Because earthworms are hermaphrodites, they can also reproduce on their own, without ever coming into contact with a mate.