ON SOME ODD FISHES.

A very singular little group of fishes is that known to the naturalist by the name Lophobranchii; this term meaning literally 'tuft-gilled.' Included in this division are two curious families, of one of which the Sea-horses or Hippocampi are the representatives; whilst to the other family belong their allies, the Pipe-fishes. No more interesting forms than these two groups can well be selected from the great class of which they are little known members. And the interest with which they are regarded by zoologists extends beyond the mere investigation of their outside form or appearance; since they present, in many points of their economy and habits, very marked deviations from what one may call the ordinary run of fish-life.

To visitors to the great aquaria which are now springing up in every part of the country, the Sea-horses will be familiar. Their hardy nature together with their curious appearance have marked them out as aquarium favourites; and they may fairly, in respect of their zoological fame, divide the honours with any of their companion-tenants. Imagine a little body from four to six inches in length, topped by a head which in outline exactly resembles that of a horse, and tapering off below or behind into a lithe, flexible, and pointed tail, and we may form a rough idea of the general appearance of one of the Sea-horses. This little body we shall find to be covered with plates or scales of hard horny or bony material, exhibiting ridges and angles all over its surface. A pair of large brilliant eyes, each of which may be moved independently of the other, add to the curious appearance of the head; whilst to the body itself, may be attached long streamers of sea-weed, serving to conceal the little beings as they nestle amid their marine bowers, each looking like some veritable creation mythological.

The flexible tail which terminates the body has the important office of mooring or attaching the fishes to any fixed object. As we see them in the aquarium, they are generally poised, on the tail, as it were; the latter being coiled around a bit of sea-weed, whilst the erect body and head look warily through the waters of their miniature sea. And when they detach themselves, they swim about in the erect position by means of the two pectoral or breast fins, which being placed close to the sides of the neck, project like veritable ears, and assist in rendering the equine appearance of the head of still more realistic nature. These fins move with a quick twittering motion, and propel their possessor swiftly through the water; whilst the back-fin, placed towards the hinder extremity of the body, also assists them in swimming.

Some curious points in the internal structure of the Sea-horses warrant a brief notice. As every one knows, the red gills of an ordinary fish are shaped each like a comb, the teeth of the comb being represented by the delicate processes, each consisting in reality of a network of blood-vessels, in which the blood is exposed to the oxygen of the water, and is thus purified. In the Sea-horses, however, the gills do not present this comb-like appearance, but exist in the form of separated tufts or bunches of delicate filaments, which spring from the gill-supports or arches. From this peculiarity, the name 'tuft-gilled,' already alluded to, is derived, and the Pipe-fishes agree in the structure of the gills with the Sea-horses. Then, also, as most readers are aware, the gills of ordinary fishes are covered by a horny plate, appropriately named the gill-cover, and it is by sharply compressing the gills with this cover, that the water used in breathing is ejected from the gills, so as to make room for a fresh supply. In the Sea-horses, however, the gill-cover is not open or free at its under and hinder edges, but is firmly attached all round to the neighbouring tissues, and so rendered immovable. But at one point in its circumference, a small aperture is left, through which the breathing water escapes from the gills.

The Sea-horses are found abundantly in the English Channel, around the coasts of France and Spain, in the Mediterranean Sea, and in the tropical oceans. A goodly number of different species are known to zoologists, but they all resemble one another in the essential features just noted. They are intelligent lively little creatures, learning in time to know the hand that feeds them. Fixed by their tails, they may be seen actively to dart the head at any passing object adapted for food. Whilst, when they wish to free their bodies from the attached position, they appear to manœuvre with the chin and head in order to effect their purpose. Their food appears to consist of small crustaceans, worms, and others of their marine neighbours, and they are known to be especially fond of such delicate tit-bits as are afforded by the eggs of other fishes.

Perhaps the most curious part of the history of the Sea-horses relates to their care of the young. Fishes generally take little or no care of their offspring, and it is therefore the more surprising to encounter in the little beings before us, a singular example of parental fidelity and attachment. Nor, as might be expected, is it the mother-fish who is charged with the task of attending the young. Contrary to the general rule, the male fish assumes the part of nurse, and well and faithfully does he appear to discharge his duties. At the root of the tail in the male Sea-horses, a curious little pouch is seen. In this pouch the eggs laid by the females—which do not possess a pouch—are deposited, and are therein duly hatched. Nor does the parental duty end here; for after the young are hatched and swim about by themselves, they seek refuge in the pouch during the early or infantile period of their life whenever danger threatens them. This procedure forcibly reminds one of the analogous habits of the kangaroos and their young; but the occurrence is the more remarkable in the lower and presumably less intelligent fish.

Some experiments made on Sea-horses seem to demonstrate the existence of a more than ordinary degree of attachment to their young. Thus when a parent-fish was taken out of the water, the young escaped from the pouch; but on the parent being held over the side of the boat, the young at once swam towards him, and re-entered the pouch without hesitation. Some authorities have not hesitated to express an opinion that the young are nourished within the pocket by some fluid or secretion from the pouch itself. But further observation is certainly necessary before this latter opinion can be relied upon.

The Pipe-fishes are very near neighbours of the Sea-horses, and derive their name from the thin elongated shape of their bodies, together with the fact that the jaws are prolonged to form a long pipe-like snout, at the extremity of which the mouth opens. These fishes are very lively in all their movements, and dart through the water so quickly that in many cases the eye is unable to follow them. Like the Sea-horses, the male Pipe-fishes protect and tend their progeny, and exhibit an equal attachment to their young.

These latter features are also well exemplified by the familiar Sticklebacks of our ponds and streams. The latter fishes actually build nests for the reception and care of their eggs, the nests being made chiefly or solely by the males; whilst on the latter, during the process of hatching and in the upbringing of the young, devolves the chief care of protecting and looking after the welfare of the progeny. These instances of the care and duties which devolve on the males, instead of on the mother-parents, appear to reverse the more natural order, which almost universally obtains in the case of both lower and higher animals.

Of the oddities which fish-life presents, probably none are more remarkable than those of the Archer or Shooting Fishes, which inhabit the seas of Japan and of the Eastern Archipelago. When kept in confinement, these fishes may be seen to shoot drops of water from their elongated jaws at flies and other insects which attract their attention, and to strike their prey with unerring aim at distances of three or four feet. Another notable species of Shooting-fishes is the Chætodon. This latter form possesses a prominent beak or muzzle, consisting of the elongated jaws; and from this beak, as from the barrel of a rifle, the fish shoots its watery missiles at the insects which alight on the vegetation that fringes its native waters.

The old saying which compares great helplessness to the state of 'a fish out of water,' does not always find a corroborative re-echo in natural history science. As every one knows, different fishes exhibit very varying degrees of tenacity of life when removed from their native element. Thus a herring dies almost immediately on being taken out of water; whilst, on the other hand, the slippery eels will bear removal from their habitat for twenty-four hours or longer; and we have known of Blennies—such as the Shanny (Blennius pholis)—surviving a long journey of some forty-eight hours' duration, when packed amid some damp sea-weed in a box.

But certain fishes are known, not merely to live when taken out of water, but actually of themselves, and as part of their life and habits, to voluntarily leave the water, and disport themselves on land. Of such abnormal fishes, the most famous is the Climbing Perch or Anabas scandens of India, which inhabits the Ganges, and is also found in Asiatic ponds and lakes. These fishes may be seen to leave the water, and to make their way overland, supporting themselves in their jerking gait by means of their strong spiny fins. They appear to migrate from one pool to another in search of 'pastures new,' especially in the dry season, and when the water of their habitats becomes shallow.

The Hindu names applied to these fishes mean 'climbers of trees;' and although statements have been made both by travellers and natives, that the Climbing Perch has been found scaling the stems of trees, these accounts, we fear, must be regarded as of equal value with the native belief that the fishes fall in showers on the land 'from the skies!' Of the power of the fishes to live for five or six days out of water, however, no doubt can be entertained; and their ability to support life under these unwonted conditions, is explained by the fact that certain bones of the head are curiously contorted so as to form a labyrinth, amid the delicate recesses of which a supply of water is retained, for the purpose of keeping the gills moist.

The curious Lepidosirens or Mudfishes, which occur in the Gambia of Africa and the Amazon of South America, exhibit a greater peculiarity of structure which still more completely fits them for living out of water. In the great majority of fishes, a curious sac or bag known as the swimming or air bladder is found. The use of this structure in ordinary fishes is to alter the specific gravity of the animals; and, by the compression or expansion of the air or gases it contains, to enable them to sink or rise in the water at will. In the Mudfishes, however, the air-bladder becomes divided externally into two sacs, whilst internally each division exhibits a cellular structure resembling that seen in the lungs of higher animals. Then also, this elaborate air-bladder communicates with the mouth and throat by a tube, which corresponds to a windpipe. The nostrils of the Mudfishes further open backwards into the mouth; whilst in all other fishes, except in one genus, the nostrils are simple, closed, pocket-like cavities. And it may lastly be noted that the Lepidosirens are provided with true gills, like their ordinary and more commonplace neighbours.

These remarks serve to explain the 'reason why' these fishes can exist for months out of water. Thus, on the approach of the hot season, the Mudfishes leave their watery homes, and wriggle into the soft mud of their rivers. Here they burrow out a kind of nest, coiling head and tail together; and as the mud dries and hardens, the fishes remain in this temporary tomb, breathing throughout the warm season like true land-dwellers, by means of the lung-like air-bladder. When the wet season once more returns, the fishes are aroused from their semi-torpid state by the early rains moistening the surrounding clay; and when the pools and rivers once more attain their wonted depth, the Lepidosirens emerge from their nests, seek the water, breathe by means of their gills, and otherwise lead a true aquatic existence.

With such a combination of the characters of land and water animals, it is little to be wondered at that the true position of the Mudfishes in the zoological scale should have formed a subject for much discussion. They appear, however, to be true fishes, and not amphibians, and they therefore may legally occupy a prominent position among the oddities of their class.

Other curious beings included among the fishes are the so-called Globe-fishes (Diodon, &c.), which derive their name from their power of distending their bodies with air at will; and their bodies being usually provided with spines, they may be judged to present a rather formidable front to any ordinary adversary, in their expanded condition. Then also we have the curious Trigger-fishes (Balistes), so named from the prominent pointed spine in front of the first of the back-fins; this spine firmly holding its erect position until the second spine or fin-ray be depressed, when the first spine is released by mechanism resembling that of the trigger of a gun. The obvious use of such an apparatus is clearly of a defensive kind; and it is remarkable to find a familiar mechanical appliance of man so accurately reproduced in the fish—or rather, vice versâ.

Printed and Published by W. & R. Chambers, 47 Paternoster Row, London, and 339 High Street, Edinburgh.

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Transcriber's Note—The following correction has been made to this text: on page 73, "torwards" changed to "towards".