* When the female population is scarce, the Bidder's organ enlarges and produces viable oocytes and then gonadotropins, which stimulate the growth of the Müllerian ducts to form uterus and oviducts. | * When the female population is scarce, the Bidder's organ enlarges and produces viable oocytes and then gonadotropins, which stimulate the growth of the Müllerian ducts to form uterus and oviducts. |