Sponges, or poriferans, reproduce both sexually and asexually. Asexually, reproduction is achieved by way of budding, which is a process in which new sponges grow out of adult sponges. It may also be achieved asexually by fragmentation, in which a detached piece of an adult sponge develops into a new organism.
Most sponges are hermaphrodites, possessing both eggs and sperm. Despite this, sexual reproduction most often occurs between sponges, as opposed to within a single organism. Sperm cells are released into the water and, depending on the species, fertilization may take place either inside or outside of another sponge's body. Once fertilized, the eggs develop into larvae, or parenchymula, which then seek a surface in open water on which to grow into an adult sponge.