Natural History, Reptiles/Amphipneusta
ORDER III. AMPHIPNEUSTA.
(Doubly-breathing Reptiles.)
In these animals the body is much lengthened, and adapted for swimming; the limbs are small, feeble, and far removed from each other, and in some species the hind pair are wanting. The tail is compressed, and remains through life. The respiration is performed in a two-fold manner, in water by means of gills, which are external, and continue throughout the whole term of existence, and in air, by means of lungs, likewise permanent. The eyes are furnished with eyelids.
The term Amphibia, having reference to the two-fold medium and manner in which is carried on the most important function of life, the renewing of the vitality of the blood, is with literal strictness applicable to these singular forms: for it is descriptive, not of a preparatory and rudimentary condition of existence, but of that which, subsisting through life, is truly proper to the animal. “The simultaneous existence and action of branchial tufts and lungs in these animals,” observes Cuvier, “can no more be contested than the most certain facts of natural history; I have before me the lungs of a Siren of three feet in length, where the vascular apparatus is as much developed and as complicated as in any reptile: nevertheless this Siren had its branchiæ as complete as the others.” Cuvier further observes that whilst the branchiæ subsist, the aorta, in coming from the heart, is divided into as many branches on each side as there are branchiæ. The blood of the branchiæ returns by the veins, which unite towards the back in a single arterial trunk, as in the fishes; it is from this trunk, or immediately from the veins which form it, that the greatest part of the arteries which nourish the body, and even those which conduct the blood for respiration in the lung, spring. But
SKELETON OF SIREN.
in the species which lose their branchiæ naturally, the branches which go there become obliterated, except two which unite in a dorsal artery, and of which each gives off a small branch to the lung. “It is,” adds this eminent comparative anatomist, “the circulation of a fish metamorphosed into the circulation of a reptile.”
The same author observes that it had been objected that it would be impossible for these animals to respire air without ribs or diaphragm, and without the power possessed by the tortoises and frogs to cause it to enter by the nostrils, in order that, so to speak, it might be swallowed, because the nostrils of the Sirens do not lead into the mouth, and the branchial apertures must let it escape. But his own observations, made upon well-preserved individuals, showed Cuvier that the nostrils in the Siren do communicate with the mouth by a hole pierced as in the Proteus, between the lip and the palatal bone which carries the teeth. The membranous opercula of their branchiæ are muscular internally, and capable of hermetically sealing the apertures; then it is very easy for the Siren, by dilating its throat, to introduce the air into the mouth, and to force it afterwards, by contracting the throat, into its larynx. Even without this structure of the nostrils, the animal could produce the same effect by opening its lips a little: a theory which Cuvier applies to the Proteus as well as the Siren.
Professor Owen has contributed some interesting observations to the Penny Cyclopædia,[1] on the size of the blood-disks (commonly called globules) in the Amphibia as compared with other animals. Their size in these Reptiles is very great, and their magnitude seems to bear a proportion to the permanency of the external gills, or branchiæ. In the double-breathing animals before us, the Sirens and Protei, these disks are so large as to be distinguishable even with the unassisted eye, while their appearance under a microscope is exhibited in the accompanying figures. The large oval figures exhibit their form as seen directly and sideways; the smaller ones represent the human blood-disk for the purpose of comparison; both are magnified seven hundred times in linear dimensions. The blood from which the former figures were taken was
BLOOD-DISKS OF SIREN AND OF MAN.
obtained from one of the external gills of a Siren lacertina twenty inches in length, which was then (1841) living at the Zoological Gardens, Regent’s Park. Though subjected to examination immediately, the large figure shows, in the crossing lines, traces of folds produced by the partial drying of the external capsule.
The species contained in this Order are very few, and compose but a single Family, Proteidæ; they are rather large animals, of dull sluggish manners, much resembling eels in form, with minute rudimentary feet, inhabiting the mud of lakes, in America and Europe. They subsist on worms, and probably other soft-bodied animals, which they find in the mud or water.
Genus Proteus (Laur.).
In this genus, which, from the singularity of its structure and appearance, and still more from the
SKULL OF PROTEUS.
anomalous character of the situation in which it is found, has excited great interest among zoologists, there are four short limbs, each pair greatly separated from the other, of which the fore feet have three toes, and the hind only two: the tail is vertically compressed, so as to form a swimming organ; the muzzle is lengthened and depressed; both jaws are furnished with minute teeth; the tongue is but slightly moveable, free at the anterior part: the eyes are excessively small and concealed beneath the skin of the head: the ear-drum is also concealed. The skeleton has considerable resemblance to that of the Salamanders, but the conformation of the skull is different; and the vertebræ are much more numerous, while the rudimentary ribs are fewer. The skin is smooth, viscid, and colourless. The branchiæ project from each side of the neck in the form of tufts, of a crimson hue.
The European Proteus (Proteus anguinus, Laur.) is much like an eel with minute feet, and is one of the most interesting links in the chain of animated nature, connecting the Reptiles with the Fishes. The deep and dark subterranean lakes of Austria are the only locality in which this singular creature has yet been discovered. One of the most romantic and
PROTEUS.
splendid caverns in Europe is the Grotto of the Magdalene, near Adelsburg, in the duchy of Carniola. The whole of that region consists of bold craggy rocks and mountains of limestone formation, perforated with spacious branching caverns, in whose awful recesses sleep the sluggish waters of vast subterranean lakes, whence many rivers take their origin. In these dreary reservoirs, over which a gleam of light has never played, save when the torch of the inquisitive traveller is flashed back from the unruffled surface, are found many Protei, swimming through the waters, or burrowing in the mud which is precipitated by them.
Nearly all that is known of these strange tenants of the bowels of the earth is comprised in the following extract from Sir Humphrey Davy's “Consolations in Travel,” where the appearance of the Protei is graphically described. In a conversation supposed to take place in the magnificent cavern above-named, Eubathes, one of the speakers, says, “I see three or four creatures, like slender fish, moving on the mud below the water.”
“The Unknown.—‘I see them; they are the Protei; now I have them in my fishing-net, and now they are safe in the pitcher of water. At first view, you might suppose this animal to be a lizard, but it has the motions of a fish. Its head and the lower part of its body and its tail bear a strong resemblance to those of the eel; but it has no fins, and its curious branchial organs are not like the gills of fishes; they form a singular vascular structure, as you see, almost like a crest, round the throat, which may be removed without occasioning the death of the animal, which is likewise furnished with lungs. With this double apparatus for supplying air to the blood, it can live either below or above the surface of the water. Its fore feet resemble hands, but they have only three claws or fingers, and are too feeble to be of use in grasping or supporting the weight of the animal; the hinder feet have only two claws or fingers, and in the larger specimens are found so imperfect as to be almost obliterated. It has small points in the place of eyes, as if to preserve the analogy of nature. It is of a fleshy whiteness and transparency in its natural state, but when exposed to light its skin gradually becomes darker, and at last gains an olive tint. Its nasal organs appear large; and it is abundantly furnished with teeth, from which it may be concluded that it is an animal of prey; yet in its confined state it has never been known to eat, and it has been kept alive for many years by occasionally changing the water in which it was placed.’
“Eubathes.—‘Is this the only place in Carniola where these animals are found?’
“The Unknown.—‘They were first discovered here by the late Baron Zoïs; but they have since been found, though rarely, at Sittich, about thirty miles distant, thrown up by water from a subterraneous cavity; and I have lately heard it reported that some individuals of the same species have been recognised in the calcareous strata in Sicily.’
“Eubathes.—‘This lake in which we have seen these animals is a very small one; do you suppose they are bred there?’
“The Unknown.—‘Certainly not; in dry seasons they are seldom found here, but after great rains they are often abundant. I think it cannot be doubted that their natural residence is in an extensive subterranean lake, from which in great floods they sometimes are forced through the crevices of the rocks into this place, where they are found; and it does not appear to me impossible, when the peculiar nature of the country in which we are is considered, that the same great cavity may furnish the individuals which have been found at Adelsburg and at Sittich.”
Observations on the living animal, as well as the study of its anatomy, render it certain that it is in a perfected condition, and not, as has been supposed, the larva or tadpole of some large unknown Triton or Salamander inhabiting those Tartarean recesses. It has been found of various sizes, from the thickness of a quill to that of a man's thumb, but the form of the respiratory organs has always been the same. Its whole comparative anatomy forbids the conclusion that the form in which we see it is that of a creature in a state of transition. Professor Wagner, who had an opportunity of dissecting a male and a female, immediately after death, observes (in some notes communicated to the Zoological Society, November 1837) that he has no doubt that the pulmonary sacs or vesicles really perform the function of lungs. Each lung contains a large artery and a still larger vein, which are connected together by means of large and numerous vessels. He found the ova in the female very beautifully developed; their structure, as well as that of the ovary, corresponding perfectly with that of the other naked Amphibia, especially the Triton. It is an animal in fact well calculated to exalt our views of the greatness of God, who is able to produce and perpetuate animal life, and doubtless enjoyment, in situations, which we should at first suppose to be barren wastes, incapable of sustaining organized existence. But it suggests curious speculations of the wonders that may exist in the bowels of our globe, of which man has as yet no knowledge.
The Proteus has been frequently brought alive to England; the observations which have been made on them in confinement, prove their extreme susceptibility to the presence of light, the stimulus of which seems painful to them. “We have always noticed,” says Mr. Martin, “that they shrouded themselves in the darkest part of the vessel in which they were placed, when the covering was taken off in order to inspect them; and that they betrayed a sense of uneasiness by their actions, when exposed to the light of open day, creeping round the sides of the vessel, or under the shelter of any substance, which threw a partial shadow on the water. . . Though these animals lived many months, and were healthy and vigorous, they were not supplied with any food, nor know we on what they subsist, though we have every reason to believe them carnivorous.”[2] A kindred animal, the Siren of North America (Siren lacertina) kept in captivity in the Gardens of the Zoological Society, was fed on earth-worms, of which it ate a dozen and a half every other day.
In June 1847, a living Proteus was exhibited to the Linnean Society, by a gentleman who had had it in his possession eighteen months. This individual had never been observed to eat.
Those specimens which have been preserved were at first of a very pale flesh-colour, with pink branchial tufts; but after a while the general hue became a light olive, and the tuft deepened into crimson.
