Aquatic macroinvertebrates of the phylum Annelida; segmented worms with bilateral symmetry, closed circulatory systems, and complete digestive systems; includes leeches. image

A phylum that includes segmented terrestrial and aquatic worms.

A class of worms in which the surface of the body exhibits a more or less distinct division into rings or segments, generally provided with appendages for locomotion and with gills. It includes the ordinary marine worms, the earthworms, and the leeches. 12