General Observations on Fishes.--Their Locomotive Organs.--Tail.--Fins.--Classification of Fishes by Cuvier.--Air-Bladder.--Scales.--Beauty of the Tropical Fishes.--The Gills.--Terrestrial Voyages of the Anabas and the Hassar.--Examples of Parental Affection.--Organs of Sense.--Offensive Weapons of Fishes.--The Sea-Wolf.--The Shark.--The Saw-Fish.--The Sword-Fish.--The Torpedo.--The Star-Gazer.--The Angler.--The Chætodon Rostratus.--The Remora, used for catching Turtles.--Defensive Weapons of Fishes.--The Weever.--The Stickleback.--The Sun-Fish.--The Flying-Fish.--The numerous Enemies of the Fishes.--Importance and History of the Herring Fishery.--The Pilchard.--The Sprat.--The Anchovy.--The Cod.--The Sturgeons.--The Salmon.--The Tunny.--The Mackerel Family.--The Eel.--The Murey.--The Conger.--The Sand-Launce.--The Plectognaths.--The Sea-Horse.--The Pipe-Fish.--The Flat-Fishes.--The Rays.--The Fecundity of Fishes. The bosom of the ocean is full of mysteries; it conceals a whole world of curiously-shaped animals, which the naturalist only superficially knows, and may, perhaps, never be able to fathom. To observe the habits of terrestrial animals, and accurately to determine their various species, is a comparatively easy task; but the denser element in which fishes live prevents us from following their motions with exactness, from studying their instincts, and from noting with fidelity their specific differences. Since Pliny, who mentions but seventy-four different kinds of fishes, the number of known species has indeed enormously increased. The ancients, who knew only the waters of the Mediterranean and a very small part of the ocean, had no conception of the finny multitudes inhabiting the tropical and icy seas; but although modern science has succeeded in describing and picturing above eight thousand different kinds of fishes, yet there can be no doubt that many still unknown species dwell in the depths of ocean, or in the distant seas which are but seldom visited by the European mariner. If the whole economy of the world of fishes were opened to our view, the magnificent picture would, no doubt, give us additional reasons for admiring the infinite wisdom of the Creator; but the little we do know suffices to convince us that the same wonderful harmony existing between the anatomical structure and the outward relations or mode of life in birds and mammiferous quadrupeds is also to be found in fishes, and that these creatures, though occupying a lower grade in Creation, are no less beautifully adapted to the peculiar element in which they are destined to live and move.