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Loeb attributes the blindness of cave fishes to a disturbance in the circulation and mutation of the eyes originally occurring as a mutation. But how could an explanation of this kind be applied to the case of Anableps tetrophthalmus, in which each eye is divided by a partition of the cornea and lens into an upper half adapted for vision in air and a lower half for vision in water?
The fish, in fact, always swims with its eye half out of the water, and it can see as well on dry land as in its native ocean. Its name is Anableps, but in all probability it does not wish the fact to be generally known. The flying fish are fish out of water in a somewhat different and more transitory sense.
A membraneous fold, enclosing the bulb of the eye, stretches across the pupil, dividing the visual apparatus into the upper and lower half; a curious formation, suited to the peculiar habits of the anableps.
They could not have been jammed artificially into the hollow wood in that way without injuring them. We have heard of blind fish, but here is one called by the Indians tralhote, and known to naturalists as the Anableps tetraophthalmus, signifying "four-eyed" possessing four eyes.
I end here this catalogue, which is somewhat dry perhaps, but very exact, with a series of bony fish that I observed in passing belonging to the apteronotes, and whose snout is white as snow, the body of a beautiful black, marked with a very long loose fleshy strip; odontognathes, armed with spikes; sardines nine inches long, glittering with a bright silver light; a species of mackerel provided with two anal fins; centronotes of a blackish tint, that are fished for with torches, long fish, two yards in length, with fat flesh, white and firm, which, when they arc fresh, taste like eel, and when dry, like smoked salmon; labres, half red, covered with scales only at the bottom of the dorsal and anal fins; chrysoptera, on which gold and silver blend their brightness with that of the ruby and topaz; golden-tailed spares, the flesh of which is extremely delicate, and whose phosphorescent properties betray them in the midst of the waters; orange-coloured spares with long tongues; maigres, with gold caudal fins, dark thorn-tails, anableps of Surinam, etc.
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