Any member of a phylum (Annelida) of invertebrate animals that possess a body cavity (coelom), movable bristles (setae), and a body divided into segments by crosswise rings. Known as segmented worms, annelids are divided into three classes: marine worms (Polychaeta; see polychaete), earthworms (Oligochaeta), and leeches (Hirudinea).
Body plan of an earthworm. Partitions (septa) divide the body cavity (coelom) into more than 100
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