(i) They are primitive animals.
(ii) They are generally multicellular organisms with specialised cells but these cells do not group together to form tissues.
(iii) Most of them are marine, i.e., found in the seas. Some of them are also found in ponds and rivers.
(iv) They possess pores all over the body.
(v) Reproduction can be by both sexual and asexual methods.
(vi) Sensory system is absent.
(vii) Mouth and anus are absent.
(viii) A distinct canal system with inlets and outlets for water circulation inside the body is present. They obtain food and oxygen by means of water. The collar cells filter out food particles from the water current flowing through the canal system.
Examples are: Sycon, Spongilla and Euplectella.
