Seahorses, which are fish, reproduce by a curious system. The female lays the eggs in a bag that the male has on the abdomen. Once in the bag, the male fertilizes the eggs with his sperm and takes care of them until hatching occurs. When this happens, the male has a real birth: the bag opens at the top and, thanks to the contractions of the abdomen, the newborn seahorses go outside.
Snails are gastropod mollusks, that is, invertebrates. They are hermaphrodites, which means that they produce as many ovules as sperm, but they cannot fertilize themselves so they copulate as many other animals do. Then they lay the fertilized eggs in soil holes or on the surface, depending on the species.