PHYLUM - ANNELIDA
Free living found in moist soil (Terristrial), fresh water or marine but few are parasite.
Body is soft elongated, cylindrical and divided into segments or metameres by ring like grooves called Annuli.
They are bilaterally symmetrical, triploblastic and have organ system level of organisation with tube within tube body plan.
They are metamerically segmented and coelomate animals.
Circulatory system is closed type
.Excretory organ is Nephridia (sing. nephridium). They also help in osmoregulation
Nervous system consists of a nerve ring (Brain) and a solid, double and ventral nerve cord with ganglia.
Reproduction is sexual,Nereis is dioecious but earthworms and leeches are monoecious.