Night crawlers also mate on the surface. They are hermaphroditic but do not self-fertilize. Following mating, each worm forms a tiny, lemon-shaped cocoon out of a liquid secreted from its clitellum, the familiar-looking bulge seen near the first third of the earthworm’s body. The sperm and egg cells are deposited inside the cocoon, and it is buried. After a two- to four-week gestation period, the baby worms emerge.