Also called APLECENTAL VIVIPARITY. Producing eggs that hatch within the mother. Animals that carry eggs internally and produce young or larvae without an external shell. The young are held within an egg casing inside the adult that thins to the point that only a thin mucus membrane remains when the young are born, or is broken upon delivery. Usually, the young have already emerged from the membrane upon delivery, appearing as a "live birth". However, because the young have hatched from an egg, although internally within the mother, this is not a true live birth. Animals that are true live-bearers are called viviparous. Ovoviviparous animals are not nourished from the mother via a placenta. OVIPAROUS, and VIVIPAROUS.