Most of them line up to form a network of canals covered with tiny, beating hairs. These hairs move water into the sponge through pores at the surface, and out through holes. Although some sponges grow to immense size, reaching more than six feet in diameter, they can still eat only food no larger than what one cell can swallow at a time. That's one disadvantage of not having a stomach. Another item sucked in by the sponge's continual current is sperm from other sponges.
Most sponges are hermaphrodites, each individual bearing both eggs and sperm.
Sperm gets shot out through one of the sponge's openings, then inhaled by another and transferred to its eggs. There, the fertilized eggs remain protected and fed. When mature, the youngsters get ejected, swimming until they find suitable sites to settle down and become full-fledged sponges. But that's not the only way sponges reproduce, and herein lies the answer to my reader's question. If you press a sponge through a fine silk cloth, the sponge's cells fall out singly.