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Annelida
Annelids are bilaterally symmetrical animals with a circulatory system and a complete digestive tract, with the mouth and anus at opposite ends of the body. They have a well developed coelem (body cavity) which forms a fluid-filled space between the digestive tract and the outer body wall. The body cavity also serves as a kind of skeleton against which muscles can operate, so it is important in burrowing, crawling, and swimming, as well as in extension and retraction of certain feeding structures. (Kozloff, 2000)
References:
Brusca, R.C., and Brusca, G.J. (2003). Invertebrates. Library of Congress Cataloging-in-Publication-Data: USA.
Kozloff, Eugene N. (2000). Seashore Life of the Northern Pacific Coast. University of Washington Press: Seattle and London.
Last updated Monday, July 17, 2006, by Administrator
