After two or three years of life, Echinoderms typically reach maturity. When this time comes, they reproduce by exeternal fertilization. In most species, the sexes are seperate in which sperm is produced in the testes and eggs are produced in the ovaries. Both types are gametes are shed and excreted into open water where fertilization then takes place. The release of sperm and eggs is sometimes coordinated in a species, but sometimes random in others. While the vast majority of Echinoderms externally fertilize, internal fertilization has been recorded for 3 brittle star species, 3 sea star species and one sea cucumber variation. The feather star and some urchins and sea cucumbers, realease their eggs normally, but then once fertilized the embryos develop in special breeding bags. Also, asexual reproduction has been observed in some species. Sea stars can regenerate lost arms, while sea cucumbers can regrow organs.