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Page:Popular Science Monthly Volume 21.djvu/402

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had been swallowed, it proved. . . to have a diameter several times exceeding that of its enemy, whose stomach it had distended to an unnatural and painful degree." The action performed by the fish in these cases is not, however, a real swallowing, but more like the similar process executed by serpents.

The interest of Dr. Günther's book does not end with the account of deep-sea fishes, but the chapters devoted to that subject and to classification illustrate the most striking discoveries that have been recently made in ichthyology. Among the curiosities of fish-life that please and amuse as well as instruct, is the story of the fighting-fish of Siam, which, on seeing another of its species, or even its own image, in a mirror, becomes suddenly excited, and of which, though it is dull in hue at other times, "the raised fins and the whole body shine with metallic colors of dazzling beauty, while the projected gill-membrane, waving like a black frill round the throat, adds something of grotesqueness to the general appearance." The Siamese are infatuated with the combats of these fishes, staking on the results considerable sums, and sometimes their persons and families, while the license to exhibit fish-fights is farmed, and brings in no small revenue to the royal treasury.

The peculiarity of the flounders, and other flat fishes, by which the eyes, normally situated in the young, move around as the animal grows, until they are both on the same side of the body, is well known, but the manner in which the transposition is effected is still in question. There is, moreover, no end to the wonders to be found in fishes' eyes. Those of the genus Anableps, known in Demerara as "four eyes," have the iris horizontally divided by a black band, which almost justifies their name; and as these fishes frequently swim with the head half out of the water, it is presumed that the upper and lower portions of the cornea are adapted for the different density of the media in which they are respectively used. The "star-gazers" (Uranoscopus), and others, have eyes that can be raised or lowered at will; but the most remarkable instance of mobility in these organs seems to exist in certain gobies of the genus Periophthalmus and its ally Boleophthalmus, which might be called "oglers," as they have the power of thrusting their eyeballs far out of the socket, and turning them as freely as a chameleon rolls his. These fishes are also remarkable for another faculty, toward which their versatile eyes must contribute not a little. At low water they remain on the muddy flats, and hunt for their prey, which consists of small crustaceans and other marine animals, making rapid leaps by the aid of their fins and tails, which are strong; and when their eyes are retracted they are protected by a membranous lid.

Then the fishes that travel over land, the flying-fishes, with the controversy as to whether they really fly or only seem to (with Dr. Günther denying the reality of the flight, and others affirming it from their personal observations), and the fish that build nests, like the