text: For example, he made some of the earliest observations about desalination: he observed early – and correctly – that when seawater is heated, freshwater evaporates and that the oceans are then replenished by the cycle of rainfall and river runoff ("I have proved by experiment that salt water evaporated forms fresh and the vapor does not when it condenses condense into sea water again.") Biology Empirical research Aristotle was the first person to study biology systematically, and biology forms a large part of his writings.He spent two years observing and describing the zoology of Lesbos and the surrounding seas, including in particular the Pyrrha lagoon in the centre of Lesbos.His data in History of Animals, Generation of Animals, Movement of Animals, and Parts of Animals are assembled from his own observations, statements given by people with specialized knowledge such as beekeepers and fishermen, and less accurate accounts provided by travellers from overseas.His apparent emphasis on animals rather than plants is a historical accident: his works on botany have been lost, but two books on plants by his pupil Theophrastus have survived.Aristotle reports on the sea-life visible from observation on Lesbos and the catches of fishermen.He describes the catfish, electric ray, and frogfish in detail, as well as cephalopods such as the octopus and paper nautilus.His description of the hectocotyl arm of cephalopods, used in sexual reproduction, was widely disbelieved until the 19th century.He gives accurate descriptions of the four-chambered fore-stomachs of ruminants, and of the ovoviviparous embryological development of the hound shark.He notes that an animal's structure is well matched to function so birds like the heron (which live in marshes with soft mud and live by catching fish) have a long neck, long legs, and a sharp spear-like beak, whereas ducks that swim have short legs and webbed feet.