text: how reptiles and amphibians lay their eggs? how reptiles and amphibians lay their eggs? the eggs are formed in the gonads of the females, that is, in the ovaries. they pass through the oviducts, where different protective layers are added, and finally go out of the female's body through the cloaca, an opening that is anterior to the tail (if they have one).  the cloaca also receives the end products of the digestive system (i.e. the feces) and the kidneys (i.e. the urine).  this process is common to all tetrapods (amphibians, "reptiles", birds and egg-laying mammals).  what happens to the unfertilized egg within the oviduct is very different in amphibians and reptiles. if you're not interested, you may stop reading here ;-)  **************************  most amphibians have external fertilization. this means that while the egg is inside the mother's body, it is still an undeveloped ovum. in some amphibian females (especially frogs and toads) the eggs are so abundant that they fill most of her abdominal cavity before they're released. they are usually released into water bodies, and the male fertilizes them as they come out.   in cecilians (legless amphibians), the males do have a copulatory organ (which acts as a penis) and fertilization of the eggs occurs within the mother's body. some of them are oviparous and lay already-fertilized eggs, but others are viviparous.  in the case of newts and salamanders, fertilization can happen in the mother's oviduct because the males produce "sperm packages" called spermatophores, which the female takes with her cloaca. then the eggs come out already fertilized; but there are also ovoviviparous and viviparous forms.  **************** now, reptiles are a different story. like us mammals, they are amniotes, which means that their eggs (as those of birds and egg-laying mammals), come out of the female body already fertilized and well on their way to development. the amniote egg is a closed "survival module" that has everything the embryo needs to survive and develop: food (the vitellum, or egg yolk), water, calcium for its bones, an air chamber, etc. encased in a tough  cover (frequently calcified).  this means that fertilization must occur _before_ the egg is laid, while the ovum is travelling along the oviduct. all amniotes have internal fertilization, and male reptiles have a penis (turtles and crocs) or paired hemipenes (lizards and snakes).   to sum up, both groups lay their eggs through the cloacal opening, but amphibian eggs need water or at least moistness to survive, because they don't have the embryonic membranes of amniotes and they lose water fast. amphibian eggs usually don't have much food either, and the embryos hatch as larvae or tadpoles that eat by themselves. in contrast, reptile embryos grow inside their extraembryonic membranes and hatch as mini-adults.