- The body surface of Annnelids is distinctly marked out into segments or metamere and, hence, the phylum name Annelida.
- They exhibit organ-system level of body organization, bilateral symmetry,they are triploblastic, metamerically segmented and coelomate animals.
- Aquatic annelids possess lateral appendages called asparapodia. For example- Nereis
- Nephridia help in osmoregulation and excretion.
- Neural system consists of paired ganglia connected by lateral nerves to a double ventral nerve cord.
- Reproduction is sexual.
- Nereis, an aquatic form, is dioecious, but earthworms and leeches are monoecious.
Examples - Nereis, Pheretima (Earthworm)