Porifera are commonly known as sponges. Sponges are characterized by the possession of an unique feeding system. Cells in the sponge walls filter nutrients and food from the water as the water is pumped through the body. The flow of this water is unidirectional, and driven by the moving flagella which line the surface of the walls connected by a series of canals. Porifera don’t have a circulatory system though. The flagellated cells on the surface of their bodies help them to obtain food and oxygen. The flagellated cells also help with the removal of waste. Since most sponges rely on the water current, they need to be living in an environment in which there is an almost constant water flow.