Answer:
phagocytosis
Explanation:
Collar cells or choanocytes are found in inner portion of sponges. They line inner portion of spongocoel in simple sponges, body wall canal in complex sponges and chambers in most complex ones.
When the water flows through these structures, collar cells generate water currents. They trap and ingest food particles like algae and water borne bacteria by phagocytosis in which the plasma membrane engulfs the food particle finally trapping it in food vacuole.
