ORGANS OF FLIGHT
Turning from this reference to the realm of mythology to existing nature, the power of flight is popularly associated with all the chief types of vertebrate animals—fishes, frogs, lizards, birds, and mammals. Many of the animals ill deserve the name of flyers, and most are exceptions to different conditions of existence which control their kindred, but it is convenient to examine for a little the nature of the structures by which this movement in the air, which is not always flight, is made possible. Certain fishes, like the lung-fish Ceratodus, of Queensland, and the mud-fish Lepidosiren, are capable of leaving the water and living on land, and for a time breathe air. But neither these fishes nor Periophthalmus, which runs with rapid movement of its fins and carries the body more or less out of water, or the climbing perch, Anabas, carried out of water over the country by Indian jugglers, ever put on the slightest approach to wings.
FLYING FISHES
FIG. 5. THE FLYING FISH EXOCŒTUS
With the fins extended moving through the air
The flight of fishes is a kind of parachute support not unlike that by which a folded paper is made to travel in the air. It is chiefly seen in the numerous species of a genus Exocœtus, allied to the gar-pike (Belone), which is common in tropical seas, and usually from a foot to eighteen inches long. They emerge from the water, and for a time support themselves in the air by means of the greatly developed breast fins, which sometimes extend backward to the tail fin. Although these fins appear to correspond to the fore limbs of other animals, they may not be moved at the will of the fish like the wing of a bird. When the flying fishes are seen in shoals in the vicinity of ships, those fins remain extended, so that the fish is said sometimes to travel 200 yards at a speed of fifteen miles an hour, rising twenty feet or more above the surface of the sea, travelling in a straight line, though sometimes influenced by the wind. Here the organ, which is at once a fin and a wing, consists of a number of thin long rods, or rays, which are connected by membrane, and vary in length to form an outline not unlike the wing of a bird which tapers to a point. The interest of these animals is chiefly in the fact that flight is separated from the condition of having lungs with which it is associated in birds, for although the flying fish has an air bladder, there is no duct to connect it with the throat.