The Handy Science Answer Book

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Animal World

Sponges, Coelenterates, and Worms

What are the major groups of segmented worms?

Members of the phylum Annelida, the segmented worms, have bilateral symmetry and a tubular body that may have 100 to 175 ringlike segments. The three classes of segmented worms are: 1) Polychaeta, the sandworms and tubeworms; 2) Oligochaeta, the earthworms; and 3) Hirudinea, the leeches.