The choanocyte (also called collar cells) line the cavity of water current (canal) of sponges. These are ovoid cells with one end embededio the mesophyll and the other exposed. The exposed end bears a flagellum, surrounded by a collar, which is made up of adjacent microvilli. The microvilli are connected to each other by delicate micro-fibrils, forming the fine Alteration device for straining food parades from the water.