As filter-feeding animals, sponges reproduce sexually and asexually. Asexual reproduction can happen when a small portion pinches, buds, or breaks off then it regenerates into a full animal. Most sponges are hermaphroditic, meaning they produce both sperm and eggs but usually at different times. With the current generated by the sponges cilia, sperm are released out of the main cavity, like a chimney and are brought through the walls of another sponge, which contain eggs. The egg is fertilized in the sponge, where it develops into a free swimming stage. It leaves the parent sponge through the central cavity, where it briefly swims, before settling. Once settled, the cells that contained the ‘tails’ to move the larvae, migrate to the interior of the body and begin to move water to the center, like a mature sponge.