Caecilians are the only order of amphibians which only use internal insemination. The male Caecilians have a penis-like organ, the phallodeum, which is inserted into the cloaca of the female for 2 to 3 hours. About 25% of the species are oviparous (egg-laying); the rest are ovoviviparous, with eggs hatching inside the mother. The eggs are guarded by the female. For some species the young caecilians are already metamorphosed when they hatch, other hatch as larvae. The larvae are not fully aquatic, but spend the daytime in the soil near the water.