In the earthworm, the cocoon is secreted by the

In the earthworm, the cocoon is secreted by the citellum. The citellum is a thickened glandular and non-segmented section of the earthworm's body that is located near the anterior end. During mating, the earthworm's body secretes a mucus that forms a ring around the worm's body, and as the worm moves forward, the ring slides towards the anterior end, picking up eggs from the ovaries and sperm from the seminal vesicles. As the mucus ring passes over the citellum, the gland secretes a thick and albuminous secretion that covers the worm's body, forming a cocoon that encloses the eggs and sperm. The cocoon then slips off the worm's body and is deposited in the soil, where the eggs develop and eventually hatch into small earthworms. Therefore, the citellum plays an important role in the reproduction of earthworms by secreting the mucus and albuminous secretion that forms the cocoon.