It is in flatworms like pleneria that we first see bilateral symmetry and sephilization the localization of the sense organs in the head region. A pair of oeli light sensitive eye spots are located toward the center of the head. Loes extending from either side of the head contain cheosensory cells. Pleneria feeds using the protrusible muscular fairings. The chemosensory cells on the loes are used to locate the food. Through rhythmic contraction of the muscular ferinx, pleneria pumps the food into the gastrovascular cavity with a siphon-like action.