DEFINITION
The Porifera may be defined as “asymmetrical or radially symmetrical multicellular organisms with cellular grade of organisation without well-defined tissues and organs ; exclusively aquatic; mostly marine, sedentary, solitary or colonial animals with body perforated by pores, canals and chambers through which water flows; with one or more internal cavities lined with choanocytes; and with characteristic skeleton made of calcareous spicules, siliceous spicules or horny fibers of spongin” .