The Romance of Natural History, Second Series

by Philip Henry Gosse

Neither of these hypotheses, then, will account for the fact: and we must admit that the fishes of these regions have the instinct to burrow down in the solid mud of the bottom, at the approach of the dry season, and the power of retaining life, doubtless in a torpid condition, until the return of the periodic rains, as Theophrastus long ago observed.[80]

The Lepidosiren, a very remarkable genus of animals from Africa and South America, affords a curious illustration of this power. It is altogether a highly singular creature, and has attracted a great deal of notice because its organisation belongs to two types: it is, so to speak, placed midway between the great classes of Reptiles and Fishes, the characters which identify it with either being almost equally balanced. Professor Owen and other eminent physiologists regard it as a fish, while Professor Bischoff, with others equally learned, consider it an Amphibian reptile.

It is the habits of this strange creature, however, which induce me to notice it here. An inhabitant of rivers and ponds, which are swollen by periodic rains, and subject to entire or partial desiccation by long droughts, it is liable to be left by the retreating waters, exposed to the burning sun, under which it would presently die, but for a special provision.

The animal has the instinct to bury itself in the mud of the bottom, on the approach of the droughts, penetrating to a depth of several feet. There it coils itself into a ball, with the tail folded over the nose, but so as to leave the nasal apertures uncovered; and, probably by its wrigglings, it forms a cavity or chamber in the clay, which becomes lined with a membranous slough thrown off from its body. Meanwhile the water evaporates, the mud dries, bakes, and cracks under the torrid heat of the dry season, thus allowing air to penetrate down to the retreat of the torpid mud-fish, in sufficient quantity for its very sluggish respiration. Here it lies inactive for five or six months, until the wet season again sets in, and the returning floods cover the old beds, soften the baked clay, revivify the imprisoned animal, and restore it to liberty and aquatic locomotion.

To meet these strange conditions of life, the Lepidosiren is furnished with a twofold apparatus for respiration; the one aquatic, consisting of gills, ordinarily contained in a branchial chamber, (but in one species, at least, external,) suited for the separation of oxygen from the water, and the other aerial, consisting of true lungs, closely resembling those of serpents, though manifestly only a modification of the well-known swim-bladder of many fishes,—by means of which the animal breathes atmospheric air, during its periodic captivity.

The same emergency is met by other species in another way. It does not appear that the Lepidosiren has the power of voluntarily forsaking the water, or of travelling on land, notwithstanding its twofold respiration; but some of the fishes of the tropics certainly resort to this mode of evading the fatal contingency of being baked out by the evaporating power of the periodical dry season.

Theophrastus, the contemporary of Aristotle, mentions fishes found in the Euphrates which in the dry seasons leave the vacant channels and crawl over the ground in search of water, moving along by fins and tail.[81] Pallegoix gives three kinds of fish in Siam, which leave the tanks and channels and travel through the grass;[82] and Sir John Bowring states that in ascending the river Meinam to Bangkok, he was amused with the sight of fish leaving the stream, gliding over the wet banks, till they disappeared among the trees of the jungle.[83] The Hydragyræ of Carolina in like manner leave the drying pools, and seek the nearest water in a straight line, though at a considerable distance. And Sir R. Schomburgk tells us that certain species of Dora in Guiana have the same habit, and are occasionally met with in such numbers in their terrestrial travels that the negroes fill baskets with them.[84]

These fishes, provincially called Hassars, project themselves on their bony pectoral fins, aiding their advance by the elastic spring of the tail exerted sidewise, proceeding in this manner nearly as fast as a man can walk. The strong scaly bands which envelop the body facilitate the march, in the same way as the transverse plates (scuta) on the belly of serpents, which take hold of the ground, as the ribs perform the office of feet. The Indians know that these fishes have the power of carrying a supply of water in a reservoir, for the keeping of the gills in a moist condition. If they fail in finding water, they are said to burrow in the still soft mud, and pass the dry season in torpidity like the Lepidosiren.

The common eel is well known to have this habit of travelling with us; I well remember my surprise, when a boy, at finding an eel in a grassy meadow one dewy summer evening, at a considerable distance from water. Since then I have seen a small species of Antennarius, running quickly to and fro on the surface of the great beds of floating sea-weed in the Gulf stream, progressing by means of its pectorals and ventrals quite out of water, with the utmost facility.