![]() ![]() A matured spermatozoon consists of a rounded nucleated head and a tail. Now these spermatogonia undergo two to three maturation divisions to form spermatocytes and these spermatocytes later give rise to spermatozoa. These cover cells are derived from other amoebocytes. This spermatogonium is surrounded by one or more flattened cover cells to form spermatocyst. The sperm mother cell or a spermatogonium is the enlarged archaeocytes. Both protandry and protogyny facilitate cross fertilization. Sponges exhibit protandry, production of sperms first and ova later or protogyny, production of ova first and sperms later. ![]() The sperm and ova are also known to be derived from choanocytes which later undergo gametogenesis to form sperm or ova. The sperm and ova are derived from the undifferentiated amoebocytes called as archaeocytes. Although sponges are bisexual (hermaphrodite) cross fertilization occurs as a rule as the production timing of sperm and ova are different. ![]() Though some unisexual sponge species are also known, most sponges are monoecious or bisexual. ![]()
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