Page:Natural History, Fishes.djvu/220

206 sort of roof formed by the side of the frontal bone; and the cornea and iris are divided by transverse bands, which give the fish the appearance of having four eyes, whereas in reality it has only two. There are certainly two openings to each eye, but still, in its essential parts, the organ is single; and whether vision is performed by the anterior or posterior opening, the same sentient organ is acted on." These remarks are confirmed by the observations of a recent naturalist, Mr. Edwards, who, in his delightful work, "A Voyage up the Amazon," thus speaks. "One curious species, the Anableps tetrophthalmus, was very common; it is called by the people, the four-eyed fish, and is always seen swimming with the nose above the surface of the water, and propelling itself by sudden starts. The eye of this fish has two pupils, although but one crystalline and one vitreous humour, and but one retina. It is the popular belief that, as it swims, two of its eyes are adapted to the water, and two to the air."

It adds to the interest of this singular little fish, that it, as well as all the other species of this group, brings forth its young alive, and in a state of considerable advancement.

2. Cobitina. Here the head is small; the body lengthened, clothed with minute scales, and enveloped in a viscous slime. The mouth is very small, placed beneath the snout, without teeth, but having thickened lips, forming a kind of sucker, and furnished with numerous fleshy cirri. The gill-openings are small, and there are but three gill-rays. There is a small dorsal situated