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Unformatted text preview: sexually mature adult while the secondary host contains the larval stage(s). The Phylum Nemertea: Ribbon Worms The phylum Nemertea include approximately 650 species of marine ribbon worms. Ribbon worms have a distinctive eversible proboscis stored in a rhynchocoel. When the walls of the rhynchocoel contract, the proboscis extends out of the body. The proboscis is a long, hollow tube that can be everted and shot outward through a pore located just above the mouth. It is used primarily for prey capture, and for defense, locomotion, and burrowing. This phylum is included as the organisms are also triploblastic. Several of the fossils from the Cambrian-aged Burgess Shale are interpreted as ribbon worms, and some extremely long worms have been found in the Mediterranean (up to 100 feet long) and in the ocean under the Antarctic ice shelves....
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- Fall '10