<Ul> <Li> Oligochaetes ("with few hairs"), which includes earthworms . Oligochaetes have a sticky pad in the roof of the mouth . Most are burrowers that feed on wholly or partly decomposed organic materials . </Li> <Li> Hirudinea, whose name means "leech - shaped" and whose best known members are leeches . Marine species are mostly blood - sucking parasites, mainly on fish, while most freshwater species are predators . They have suckers at both ends of their bodies, and use these to move rather like inchworms . </Li> </Ul> <Li> Oligochaetes ("with few hairs"), which includes earthworms . Oligochaetes have a sticky pad in the roof of the mouth . Most are burrowers that feed on wholly or partly decomposed organic materials . </Li> <Li> Hirudinea, whose name means "leech - shaped" and whose best known members are leeches . Marine species are mostly blood - sucking parasites, mainly on fish, while most freshwater species are predators . They have suckers at both ends of their bodies, and use these to move rather like inchworms . </Li> <P> The Archiannelida, minute annelids that live in the spaces between grains of marine sediment, were treated as a separate class because of their simple body structure, but are now regarded as polychaetes . Some other groups of animals have been classified in various ways, but are now widely regarded as annelids: </P>

The organ of excretion in the earthworm and other annelids