Fig. 357. The Globe-fish (Orthagoriscus), and Sun-fish (Tetrodon).
In the family of Gymnodonta the jaws have no apparent teeth, but they are furnished with a species of beak in ivory, which represents them. The Sun-fish, Tetrodon (Fig. 357), belong to the family.
The Globe-fish are so named from their large head and bony salient jaws, which are each divided in front by a sort of vertical slit in two portions, which simulate two teeth. These four portions of bony jaw, which project beyond the lips, somewhat resemble the hard and dentate jaws of the turtle. Their anterior part is sometimes prolonged, like the mandibles of the beak of the parrot. They are perfectly arranged to crush the shells of the molluscs, as well as the resisting envelope of the crustaceans on which they feed. The skin of these fishes bristles with small slightly-projecting spines, the number of which compensate for their brevity, which repel their enemies, and even wound the hand that would grasp them. They enjoy, besides, a singular faculty; they can inflate the lower part of their body, and give it an extension so considerable that it becomes like an inflated ball, in which the real shape of the animal is lost. This result is obtained by the introduction of an immense quantity of air into the stomach when it wishes to ascend to the surface. The species of globe-fish are numerous. Some of them are common in the Nile, where they are frequently left ashore during the annual inundations.
The Globe-fish (Orthagoriscus mola), in the upper part of the engraving, is easily distinguished from the Tetrodons by its compressed spineless body; being very round in its vertical contour, it has been compared to a disk, and more poetically to the moon—whence its popular names—to the great circular surface of which the dazzling silvery white disk bears some resemblance. But it is especially during the night that it justifies the name given to it. Then it shines brightly, from its own phosphorescent light, at a little distance beneath the surface. On very dark nights the globe-fish is sometimes seen swimming in the soft light which emanates from its body, the rays rendered undulating by the rippling of the water which it traverses, so as to resemble the trembling light of the moon half-veiled in misty vapours. When many of these fishes rove about together, mingling their silvery trains, the scene suggests the idea of dancing stars. The moon-fish is common in the Mediterranean, and sometimes reaches the markets of Paris. It is about thirty inches in length, and its weight is considerable. Its flesh is fat and viscous, and by no means pleasant to eat.
The Diodons (Fig. 358) only differ from the globe-fish in the form of their bony jaws, each forming only one piece. They seem to have two teeth, whence their name, from δίς, two, ὀδοὺς, teeth. They differ also in their spines, which are much larger than those of the globe-fish. These fishes may be said to be the hedgehogs and porcupines of the sea. Like the globe-fish, they can erect their spines and inflate their bodies.
They are numerous in species—Diodon pilosus, represented in Fig. 358, being typical of the others.
Fig. 358. Diodon pilosus.
