anything that is small enough to fit inside the hole of its incurrent siphon enters the bivalve. when the floating material comes in, it gets stuck in slimy mucus that is on the surface of the bivalve's gills. the food is moved down to the mouth, which is on the other side of the siphon. food is digested in the bivalve's stomach and intestine, and everything that is not digested goes out through the other siphon, with water.