Collar cells produce a constant flow of water into the sponge. Water enters incurrent canals and flows through pores within porocytes, into the flagellated canals, and on to the spongocoel. Eventually the filtered water exits through a large hole in the end of the sponge called the osculum. Choanocytes remove suspended food particles as water moves through the sponge. A specialized collar of microvilli surrounding flagella of the choanocytes traps food particles that are engulfed by the cell body.
Digestion is intracellular, meaning that it occurs inside cells.
Cnidarians are almost all marine carnivores. Their bodies are radially symmetrical and more complex than sponges. Radial symmetry describes a body from with repetitive body areas arranged in a circle around a central point such as the pieces of a pic. A gelatinous mesoglea separates the two true body layer. Polyps are usually attached to the substrate and may be solitary or colonial.