Be careful not to cut too deep or you will slice into the digestive system. (The ventral side is more flattened than the dorsal side.) Using dissecting scissors, cut through the dorsal body wall posterior to the clitellum and continue the incision toward the prostomium. Place the earthworm on its ventral side.It secretes mucus that holds 2 earthworms together during mating and produces a cocoon in which eggs and sperm are deposited for external fertilization. The clitellum is the enlarged structure that begins at segment 31.Also locate the openings to the sperm ducts on segment 15. Find the openings to the oviducts, which release eggs at segment 14, counting from the anterior end. Earthworms are hermaphroditic so both sex organs are present.You may need to use a hand lens or stereomicroscope to see these openings. Each segment also contains a pair of small excretory pores called nephridiopores.Locate the tiny bristles on the ventral surface called setae.Earthworms are annelids, or segmented worms that have bodies made up of a series of ring-like segments. Locate the mouth opening and the prostomium at the anterior end.The earthworm has no head and no appendages, but it does possess external characteristics to study. The anterior end is somewhat larger than the posterior. First, identify the anterior and posterior ends.
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