The capillaries join, forming larger vessels. Blood is returned to the aortic arches through the dorsal vessel, which runs along the top of the digestive tract. Follow it forward toward the esophagus. Gently move aside any organs that obscure your view so that you can see the aortic arches around the esophagus. Lift the cut end of the intestine so that you can see the ventral vessel, which runs along the ventral surface of the digestive tract.
Earthworms are hermaphroditic-they contain both male and female reproductive strucures.
However, self-fertilization does not occur. When earthworms mate, they exchange sperm, which later will fertilize the eggs produced by the ovaries. Sperm are produced and stored in the seminal vesicles . Sperm received from another animal in mating are stored in the two pairs of seminal receptacles . The most visible parts of the reproductive system are the pair of three-lobed seminal vesicles on either side of the esophagus.