Fig. 6.—Green Tree Frog (Hyla).
Fig. 6.—Green Tree Frog (Hyla).
The Green Tree Frog is easily distinguished by having little plates under its toes. These organs are a species of sucker, by means of which the animal is enabled, like the house-fly, to cling strongly to any surface, however smooth and polished it may be. The smoothest branch, even the lower surface of a leaf, forms a sufficient hold and support to these delicate organs.
The upper part of the body is of a beautiful green, the lower part, where little tuberculi are visible, is white. A yellow line, lightly bordered with violet, extends on each side of the head and back, from the muzzle to the hind legs. A similar line runs from the jaw to the front legs. The head is short, the mouth round, and the eyes raised. Much smaller than the ordinary Frog,they are far more graceful. During the summer they live upon the leaves of trees in damp woods, and pass the winter at the bottom of some pond, which they do not leave till the month of May, after having deposited their eggs. They feed on small insects, worms, and mollusks; and in order to catch them, they will remain in the same place an entire day. During the glare of the sun, they remain hidden amongst the leaves; but when twilight approaches, they move about and climb up the trees. We must repeat of these Green Tree Frogs what we have already said of Frogs. Get rid of all prejudice towards their kind, and then you will examine with pleasure their lively colours, which harmonize so well with the green leaves; remark their tricks and ambuscades; follow them in their little hunting excursions; see them suspended upside down upon the leaves in a manner which appears marvellous to those who are not aware of the organs which have been given to enable them to attach themselves to the smoothest bodies: and it will give as much pleasure as can be derived from the consideration of the plumage, habits, and flight of birds. The croak of the Green Tree Frogs is like that of other Frogs, although less sharp and sometimes stronger in the males; it can be pretty well translated by the syllablescaraccarac, pronounced from the throat. This cry is principally heard in the morning and evening; then, when one Frog begins to utter its croak, all the others imitate it. In the quiet night the voice of a troop of these little Batrachians sometimes reaches to an enormous distance.
Toads,Bufo, are squat and disagreeable in shape: it is difficult to comprehend why nature, which has bestowed elegance and a kind of grace upon Frogs and Tree Frogs, has stamped the Toad with so repulsive a form. These much despised beings occupy a large place in the order of nature: they are distributed with profusion, but one cannot say exactly to what end; their movements are heavy and sluggish. In colour they are usually of a livid grey, spotted with brown and yellow, and disfigured by a number of pustules or warts. A thick and hard skin covers a flat back; its large belly always appears to be swollen; the head a little broader than the rest of its body; the mouth and the eyes are large and prominent. It lives chiefly at the bottom of ditches, especially thosewhere stagnant and corrupt water has lain a long time. It is found in dung heaps, caves, and in dark and damp parts of woods. One has often been disagreeably surprised on raising some great stone to discover a Toad cowering against the earth, frightful to see, but timorous, seeking to avoid the notice of strangers. It is in these different obscure and sometimes fœtid places of refuge that the Toad shuts itself up during the day; going out in the evening, when our common species moves by slight hops; whilst another, the Natterjack Toad,Bufo calamita, only crawls, though somewhat fastly. When seized, it voids into the hand a quantity of limpid water imbibed through the pores of its skin; but if more irritated, a milky and venemous humour issues from the glands of its back.
Fig. 7.—The Common Toad (Bufo vulgaris).
Fig. 7.—The Common Toad (Bufo vulgaris).
One peculiarity of its structure offers a defence from outward attacks. Its very extensible skin adheres feebly to the muscles, and at the will of the animal a large quantity of air enters between this integument and the flesh, which distends the body, and fills the vacant space with an elastic bed of gas, by means of which it is less sensible to blows. Toads feed upon insects, worms, and small mollusks. In fine evenings, at certain seasons especially, they may be heard uttering a plaintive monotonous sound. They assemble in ponds, or even in simple puddles of water, where theybreed and deposit their eggs. When hatched, the young Toads go through the same metamorphosis as do the tadpoles of the Frogs.
Their simple lives, though very inactive, are nevertheless very enduring; they respire little, are susceptible of hibernation, and can remain for a considerable time shut up in a very confined place.
It is proper, however, to caution the reader against believing all that has been written about the longevity of Toads. Neither must implicit faith be given to the discovery of the living animal (Fig. 7) in the centre of stones. "That Toads, Frogs, and Newts, occasionally issue from stones broken in a quarry or in sinking wells, and even from coal-strata at the bottom of a mine," is true enough; but, as Dr. Buckland observes, "the evidence is never perfect to show that these Amphibians were entirely enclosed in a solid rock; no examination is made until the creature is discovered by the breaking of the mass in which it was contained, and then it is too late to ascertain whether there was any hole or crevice by which it might have entered." These considerations led Dr. Buckland to undertake certain experiments to test the fact. He caused blocks of coarse oölitic limestone and sandstone to be prepared with cells of various sizes, in which he enclosed Toads of different ages. The small Toads enclosed in the sandstone were found to die at the end of thirteen months; the same fate befell the larger ones during the second year: they were watched through the glass covers of their cells, and were never seen in a state of torpor, but at each successive examination they had become more meagre, until at last they were found dead. This was probably too severe a test for the poor creatures, the glass cover implying a degree of hardness and dryness not natural to half amphibious Toads. Moreover, it is certain that both Toads and Frogs possess a singular facility for concealing themselves in the smallest crevices of the earth, or in the smallest anfractuosities of stones placed in dark places.
This animal, so repulsive in form, has been furnished by nature with a most efficient defensive armature; namely, an acrid secretion which will be described farther on. It is a bad leaper, an obscure and solitary creature, which shuns the sight of man, as if it comprehended the blot it is on the fair face of creation. It is, nevertheless, susceptible of education, andhas occasionally been tamed; but these occasions have been rare. Pennant, the zoologist, relates some curious details respecting a poor Toad, which took refuge under the staircase of a house. It was accustomed to come every evening into a dining-room near to the place of its retreat. When it saw the light it allowed itself to be placed on a table, where they gave it worms, wood-lice, and various insects. As no attempt was made to injure it, there were no signs of irritation when it was touched, and it soon became, from its gentleness (the gentleness of a Toad!), the object of general curiosity; even ladies stopped to see this strange animal. The poor Batrachian lived thus for six and thirty years; and it would probably have lived much longer had not a Crow, tamed, and, like it, a guest in the house, attacked him at the entrance of his hole, and put out one of his eyes. From that time he languished, and died at the end of a year.
Fig. 8.—Surinam Toad (Pipa monstrosa).
Fig. 8.—Surinam Toad (Pipa monstrosa).
Nearly allied to the Toads,Bufo, the Surinam Toad,Pipa, holds its place. Its physiognomy is at once hideous and peculiarlyodd: the head is flat and triangular, a very short neck separates it from the trunk, which is itself depressed and flattened. Its eyes are extremely small, of an olive, more or less bright, dashed with small reddish spots. It has no tongue. There is only one species of Pipa, viz. the American Pipa (Fig. 8), which inhabits Guiana and several provinces of Brazil. The most remarkable feature in this Batrachian is its manner of reproduction. It is oviparous, and when the female has laid her eggs, the male takes them, and piles upon the back of his companion these, his hopes of posterity. The female, bearing the fertilized eggs upon her back, reaches the marshes, and there immerses herself; but the skin of the back which supports the eggs soon becomes inflamed, erysipelatous inflammation follows, causing an irritation, produced by the presence of eggs, which are then absorbed into the skin, and disappear in the integument until hatched.
The young Pipa Toads are rapidly developed in these dorsal cells, but they are extricated at a less advanced stage than almost any other vertebrate animal. After extrication, the tadpole grows rapidly, and the chief change of form is witnessed in the gills. As to the mother Batrachian, it is only after she has got rid of her progeny that she abandons her aquatic residence.9
The Batrachians differ essentially from all other orders ofReptilia. They have no ribs; their skin is naked, being without scales. The young, ortadpoles, when first hatched, breathe by means of gills, being at this stage quite unlike their parents. These gills, or branchiæ, disappear in the tailless Batrachians, as the Frogs and Toads, in which the tail disappears, are called. In the tadpoles the mouth is destitute of a tongue, this organ only making its appearance when the fore limbs are evolved. The habits also change. The tadpole no longer feeds on decomposing substances, and cannot live long immersed in water. The branchiæ disappear one after the other, by absorption, giving place to pulmonary vessels. The principal vascular arches are converted into the pulmonary artery, and the blood is diverted from the largest of the branchiæ to the lungs.In the meantime the respiratory cavity is formed, the communicating duct advances with the elongation of the œsophagus, and at the point of communication the larynx is ultimately developed. The lungs themselves extend as simple elongated sacs, slightly reticulated on the inner surface backwards into the abdominal cavity. These receptacles being formed, air passes into and expands the cavity, and respiration is commenced, the fore limbs are liberated from the branchial chambers, and the first transformation is accomplished.
The alleged venemous character of the Common Toad has been altogether rejected by many naturalists; but Dr. Davy found that venemous matter was really contained in follicles in the true skin, and chiefly about the head and shoulders, but also distributed generally over the body, and on the extremities in considerable quantities. Dr. Davy found it extremely acrid, but innocuous when introduced into the circulation. A chicken inoculated with it was unaffected, and Dr. Davy conjectures that this acrid liquid is the animal's defence against carnivorous Mammalia. A dog when urged to attack one will drop it from its mouth in a manner which leaves no doubt that it had felt the effects of the secretion.
In opposition to these opinions the story of a lad in France is told, who had thrust his slightly wounded hand into a hole, intending to seize a Lizard which he had seen enter. In place of the Lizard he brought out a large Toad. While holding the animal, it discharged a milky yellowish white fluid which introduced itself into the wound in his hand, and this poison occasioned his death; but then it is not stated that the boy was previously healthy.
Warm and temperate regions with abundant moisture are the localities favourable to all the Batrachians. Extreme cold, as well as dry heat, and all sudden changes are alike unfavourable to them. In temperate climates, where the winters are severe, they bury themselves under the earth, or in the mud at the bottom of pools and ponds, and there pass the season without air or food, till returning spring calls them forth.
The species of this family are very numerous. MM. Duméril and Bibron state that the Frogs,Rana, number fifty-one species; the Tree Frogs,Hyla, sixty-four; and the Toads,Bufo, thirty-five.They are found in all parts of the world, the smallest portion being found in Europe, and the largest in America. Oceania is chiefly supplied with the Tree Frogs. There are several curious forms in Australia, and one species only is known to inhabit New Zealand. The enormous fossilLabyrinthodon, of a remote geological era, is believed to have been nearly related to these comparatively very diminutive Batrachians.10
Sometimes called Urodeles, fromουρα, "tail,"δηλος, "manifest." The constant external character which distinguishes these Amphibians in a general manner is the presence of a tail during the whole stage of their existence. Nevertheless they are subject to the metamorphoses to which all the Amphibians submit. "The division, therefore, of reptiles," says Professor Rymer Jones, "into such as undergo metamorphoses and such as do not, is by no means philosophical although convenient to the zoologist, for all reptiles undergo a metamorphosis although not to the same extent. In the one the change from the aquatic to the air-breathing animal is never fully accomplished; in the tailed Amphibian the change is accomplished after the embryo has escaped from the ovum."
Salamanders have had the honour of appearing prominently in fabulous narrative. The Greeks believed that they could live in fire, and this error obtained credence so long, that even now it has not been entirely dissipated. Many people are simple enough to believe from the Greek tradition that these innocent animals are incombustible. The love of the marvellous, fostered and excited by ignorant appeals to superstition, has gone even further than this; it has been asserted that the most violent fire becomes extinguished when a Salamander is thrown into it. In the middle ages this notion was held by most people, and it would have been dangerous to gainsay it. Salamanders were necessary animals in the conjurations of sorcerers and witches; accordingly painters among their symbolical emblems represented Salamanders as capable ofresisting the most violent action of live coal. It was found necessary, however, that physicians and philosophers should take the trouble to prove by experiment the absurdity of these tales.
The skull of the Land or Spotted Salamander,Salamandra maculosa, is well described by Cuvier as being nearly cylindrical, wider in front so as to form the semi-circular face, and also behind for the crucial branches, containing the internal ears. The cranium of the aquatic Salamander differs from the terrestrial in having the entire head more oblong, and they differ also among themselves.
Fig. 9.—Land Salamander.
Fig. 9.—Land Salamander.
In the Land Salamander the body is black and warty with large irregular yellow spots distributed over the head, back, sides, feet, and tail. They affect obscure and moist places, and only issue from their retreat in the night or morning, walking slowly, and dragging themselves with difficulty along the surface of the ground. They live upon flies, beetles, snails, and earth worms. They remain in the water to deposit their eggs; the young are born alive, and furnished with fully-developed gills. Moreover Salamanders are gifted with a power which causes them to be much dreaded by other animals: it has the power of discharging an acrid and milky humour, with a very strong odour, from the surface of its body, which serves as a defence against many animals which would otherwise attack it. It has been proved by experiment that this liquid, when introducedinto the circulatory system by a small wound is a very active poison, and causes certain death to the smaller animals. This species is found in most parts of Europe, but not in the British Islands.
The Black Salamander,Triton alpestris, has no spots; it is found on the highest European mountains, in the regions of snow, and principally on the highest Alps.
Fig. 10.—Newts, or Aquatic Salamanders.
Fig. 10.—Newts, or Aquatic Salamanders.
Newts, or Aquatic Salamanders, have not a round conical tail like the terrestrial species, but have that appendage compressed or flattened laterally. The males (during the breeding season only) are recognised chiefly by the membranous serrated ridge or crest which extends along the whole length of the back, from the head to the extremity of the tail, as represented inFig. 10. Newts are highly aquatic; they are found in ditches, marshes, and ponds, which after the breeding season they leave for moist places on land, often then finding their way into drains and cellars. They are carnivorous, feeding upon different insects and on the spawn of Frogs, not even sparing individuals of their own species. The females deposit their eggs singly, fixing them on the under surface of the leaves of aquatic plants. "Some Newts," says Professor Owen, "deposit their eggs upon aquatic plants, such asPolygonum persicaria, folding the leaf by means of the hind feetin such a way that its under surface is turned inwards and the fold made to stick by the adhesive coating of the egg, which she inserts in the fold." The young are hatched fifteen days after. These animals give utterance to a very peculiar noise, and when touched emit an odour quite characteristic.
It has been ascertained that Newts can live for a long time, not only in very cold water, but even in the midst of ice, being sometimes taken in blocks of ice which are formed in the ditches and ponds which they inhabit. When the ice-flakes melt they seem to awaken from their torpor, and betake themselves to their accustomed movements with their recovered liberty. Lacépède states that he found Aquatic Salamanders even during summer in pieces of ice obtained from the ice-dealers, where they had remained without movement or nourishment from the time when the ice had been gathered from the marshes.
Newts present another remarkable feature in the facility with which they repair any mutilations they may have undergone. Not only do their tails grow again when broken off, but even their feet are reproduced in the same manner, and the process may be many times repeated.
The Crested Newt,Triton cristatus, is frequently found in the neighbourhood of Paris; the skin of its back is rough and warty, of a brownish colour, with large black spots and white projecting points; the belly has black spots upon an orange ground.
The Dutch traveller, Sieboldt, has introduced a species of Aquatic Salamander, which inhabits the mountain lakes and marshes of Japan. This species is remarkable for its gigantic growth. Instead of being the size of a finger, as is the case with those indigenous to Europe, this Batrachian is four feet and a half in length, and weighs fifty pounds.
Magnificent specimens of this gigantic Salamander, theSieboldtia maxima, may be seen by the visitors to the London Zoological Gardens. The largest of them measured and weighed as above (March 3rd, 1869). An analogous large fossil species was described as theHomo diluvii testis!
The transformation of the tailed Batrachians, from thetadpolecondition to the air-breathing and four-footed state, is one of the most interesting exhibitions of Nature, and one which everyonemay verify for himself. We cannot in our brief description have a more trustworthy guide than Professor Rymer Jones, who selects the Water Newt,Triton cristatus, as an example:—
"Immediately before leaving the egg," he says, "this tadpole presents both the outward form and internal structure of a fish. The flattened and vertical tail, fringed with a broad dorsal and oval fin; the shape of the body and gills, appended to the side of the neck, are all apparent; so that were the creature to preserve this form throughout its life the naturalist would scarcely hesitate in classing it with fishes, properly so called.
"When first hatched it presents the same fish-like body, and rows itself through the water by the lateral movement of the caudal fin. The only appearance of legs as yet visible consists in two minute tubercles, which seem to be sprouting out from the skin immediately behind the branchial tufts, and which are, in fact, the first buddings of anterior extremities. Nevertheless, to compensate to a certain extent for the total want of prehensile limbs, which afterwards become developed, two supernumerary organs are provisionally furnished in the shape of two minute claspers on each side of the mouth; by means of these the little creature holds on to the leaves which are under water.
"Twelve days after issuing from the egg, the two fore-legs, which at first resembled two little nipples, have become much elongated, and are divided at their extremity into two or three rudiments of fingers. The eyes, which were before scarcely visible, being covered by a membrane, distinctly appear. The branchiæ, at first simple, are divided into fringes, wherein red blood now circulates; the mouth has grown very large, and the whole body is so transparent as to reveal the position of the viscera within. Its activity is likewise much increased; it swims with rapidity, and darts upon minute aquatic insects, which it seizes and devours.
"About the twenty-second day the tadpole for the first time begins to emit air from the mouth, showing that the lungs have begun to be developed. The branchiæ are still large. The fingers upon the fore-legs are completely formed. The hind-legs begin to sprout beneath the skin, and the creature presents, in a transitory condition, the same external form as that which theSiren lacertinapermanently exhibits.
"By the thirty-sixth day the young Salamander has arrived at the development of theProteus anguinus; its hind-legs are nearly completed; its lungs have become half as long as the trunk of the body, and its branchiæ more complicated in structure.
"At about the forty-second day the tadpole begins to assume the form of an adult Newt. The body becomes shorter, the fringes of the branchiæ are rapidly obliterated, so that in five days they are reduced to simple prominences covered by the skin of the head; and the gills opening at the sides of the neck, which allowed the water to escape from the mouth as in fishes, and were, like them, covered with an operculum formed by a fold of the integument, are gradually closed; the membranous fin of the tail contracts, the skin becomes thicker and more deeply coloured, and the creature ultimately assumes the form and habits of the perfect Newt, no longer possessing branchiæ, but breathing air, and in every particular the Reptile."
But however curious the phenomena attending the development of the tadpoles of the Amphibian Reptiles may be to the observer who merely watches the changes perceptible from day to day in their external form, they acquire tenfold interest to the physiologist who traces the progressive evolution of their internal viscera; more especially when he finds that in these creatures he has an opportunity afforded him of contemplating, displayed before his eyes, as it were, upon an enlarged scale, those phases of development through which the embryo of every air-breathing vertebrate animal must pass while concealed within the egg, or yet unborn.11
Reptiles are, as has been said in the preceding chapter, Vertebrated Animals, breathing by lungs, having red and cold blood; that is to say, not producing sufficient heat to render their temperature superior to that of the atmosphere. Destitute of hairs, of feathers, of mammary glands, and having bodies covered with scales.
Snakes, properly so called, have the tympanic bone, or pedicle of the lower jaw, movable, and nearly always suspended to another bone, analogous to the mastoid bone, which is attached to the cranium by muscles and ligaments, a conformation which gives to these animals the vast power of distension they possess. Their trachea is long, their hearts placed far back, and the greater number have one very long lung and vestiges of a second. They are divided into non-venemous and venemous; and the latter are subdivided into venemous with maxillary teeth, and venemous with isolated fangs.
The Snakes prey almost exclusively on animals of their own killing; the more typical species attacking such as are frequently larger than themselves: and the maxillary apparatus is, as we have seen, modified so as to permit of the requisite distension. According to Professor Owen's clear and intelligible description, the two superior maxillary bones have their anterior extremities joined by an elastic and yielding fibrous tissue with the small and single intermaxillary bone; the lower maxillary rami are similarly connected. The opposite extremity of each ramus is articulated to a long and movable vertical pedicle formed by the tympanic bone, which is itself attached to theextremity of a horizontal pedicle formed by the mastoid bone, so connected as to allow of a certain yielding movement upon the cranium. The other bones have similar loose movable articulations, which concur in yielding to the pressure of large bodies with which the teeth have grappled.
The class of Reptiles is divided into three orders:—theOphidians, comprehending the Snakes; theSaurians, the Lizards and Crocodiles; and theChelonians, the Turtles and Tortoises.
In Ophidians, commonly known under the name of Snakes, the body is long, round, and straight. They have neither feet, fins, nor other locomotive extremities. Their mouths are furnished with pointed hooked teeth. In the Boas and Pythons the teeth are slender, curved, bending backwards and inwards above their base of attachment. In others each maxillary bone has a row of larger ones, which gradually decrease in size as they are placed further back. These teeth are not contiguous, being separated by considerable intervals. The smaller non-venemous Serpents, such as theColubridæ, have two rows of teeth in the roof of the mouth. Each maxillary and mandibular bone includes from twenty to twenty-five teeth. In the Rattlesnakes and some other typical genera of poisonous Snakes, the short maxillary bone only supports a single perforated fang. Their lower jaw is highly distensible; the opening beings longer than the skull. They have no neck; their eyelids are immovable; their skin is coriaceous, highly extensible, and scaly or granulous, covered with a thin caducous epidermis, which detaches itself in one entire piece, and is reproduced several times in one year. Their movements are supple and varied. In consequence of the sinuosity of their bodies,—for, though scale-clad, Snakes are without apparent means of progression,—they make their way with the utmost facility, by walking, leaping, climbing, or swimming.
According to the genus chiefly, the very numerous species inhabit either arid or moist places, the ground, or bushes and trees. Some pass much of their time in the water, and one family (that of theHydrophidæ) is exclusively aquatic—evenpelagic in the instance of one very widely diffused species, thePelamis bicolor. In the Arboreal Snakes the tail is very long, and highly prehensile; in others, as the Vipers, it is short and without any prehensility. In the Sea Snakes (Hydrophidæ), it is laterally much compressed. Like other true reptiles, Snakes abound more especially in warm climates, and there are many kinds of them in Australia; but the order has not a single representative in New Zealand.
Most of the Snakes feed on living animals, only a few on birds' eggs. Several kinds of them prey habitually on other Snakes, as the generaHamadryas,Bungarus, andElaps, evenPsammophisoccasionally; and there are rare instances of non-venemous Snakes preying upon poisonous ones. The venemous kinds first kill their victim by poisoning it; various others by smothering it between the coils of their body. As they do not possess organs for tearing the prey to pieces, nor a dentition fit for mastication, the prey is swallowed entire; and in consequence of the great width of the mouth, and of the extraordinary extensibility of the skin of the gullet, they are able to swallow animals of which the girth much exceeds their own. The Sea Snakes prey mostly upon fishes, and the ordinary Water Snakes (Homolopsidæ, &c.) on frogs and other Batrachians. Certain swallowers of birds' eggs have peculiar spinous processes proceeding from the vertebræ of the neck, the object of which is to fracture the shell of an egg during the process of deglutition.
Most of the Ophidian Reptiles are oviparous, but many are ovo-viviparous. The Pythons alone (so far as ascertained) perform a sort of incubation, which has been repeatedly observed of captive specimens of these huge Serpents.
Many Snakes are remarkable for their great beauty of colouring, or of the pattern of their markings; but on account of the poisonous property of so many of them, the whole order is popularly regarded with horror and apprehension, and the most foolish tales are current respecting various species of them. Thus many people suppose that there are Snakes which rob cows of their milk; and the skeleton of a child being found in the same hollow with a number of harmless Snakes (the North AmericanCoryphodon constrictor), it was concluded, as a matter of course,that the Serpents must have both killed the child and stripped off its flesh, which latter is what no Snake could possibly do. People are prone to exaggerate, and commonly evince a fondness for the marvellous, which induce those of hot countries more especially, where the species of Ophidians are numerous, to declare every Snake met with as usually the most venemous one in their country; and thus travellers often come away with exceedingly erroneous impressions on the subject. The Indian region surpasses every other part of the globe in the number and variety of its Ophidians, and almost every investigation of a limited but previously unexplored district, is tolerably sure to add largely to our previous knowledge of them. What, however, the late Sir J. Emerson Tennent asserts of those inhabiting Ceylon, is equally applicable to other parts of the Indian region. "During my residence in Ceylon," he remarks, "I never heard of the death of an European which was caused by the bite of a Snake; and in the returns of coroners' inquests made officially to my department, such accidents to the natives appear chiefly to have happened at night, when the reptiles, having been surprised or trodden on, inflicted the wound in self-defence. For these reasons the Cingalese, when obliged to leave their houses in the dark, carry a stick with a loose ring, the noise of which, as they strike it on the ground, is sufficient to warn the Snakes to leave their path."
In some parts of the vast Indian region the natives regard the innocuous Chameleon as venemous; in other parts various Geckos, or other Lizards. In Bengal there is a current notion regarding a terrifically poisonous Lizard, which is termed theBis-cobra, but which has no existence except in the imagination of the natives—who bring the young of the Monitors and occasionally other well-known Lizards as exemplifying the object of their dread. Again, the little harmless Burrowing Snakes (Typhlops), which, superficially, have much the appearance of earth-worms, are there popularly regarded as highly poisonous, though not only are they harmless, but physically incapable of wounding the human skin. Strangers who are little versed in zoology are commonly led astray by such errors on the part of natives of those countries, and, unfortunately, there is a number of stock vernacular names which are applied to very different species in different localities. Thus Europeansin India are familiar with the appellation "Carpet Snake," as denoting a very deadly reptile, but nobody can there point out what the Carpet Snake really is; and the one most generally supposed to bear that name is a small innocuous Snake (Lycodon aulicus), which is common about human dwellings. In the Australian colony of Victoria, however, the appellation Carpet Snake is bestowed upon a terribly venemous species (Hoplocephalus curtus); while in the neighbouring colony of New South Wales, a harmless and even useful creature (Morelia spilotes) is habitually known as the Carpet Snake.
With regard to the poison of Venemous Snakes, attention has lately been directed to the virtue of ammonia or volatile alkali. This should be administered internally, mixed with alcoholic spirit and water, in repeated doses; and it should also be injected into a vein—about one drachm of theliquor ammoniæof the shops being mixed with two or three times that quantity of water. The patient should be kept moving as much as possible, and the effects of a galvanic battery should also be tried in cases where animation is nearly or quite suspended. By these means it is asserted that quite recently, in Australia, some very remarkable cures have been effected.
TheOphidiahave many enemies, as the well-known Mongoose among mammalia, also Swine, and various ruminating quadrupeds, as Deer and Goats. In the bird class, the famous Serpent-eater, or Secretary-bird of South Africa, is one of their chief destroyers; and there are various other Snake-devouring birds of prey, besides the great African Ground Hornbill,—even the Pea-fowl and sundry Storks and other waders. Comparatively large birds of the King-fisher family prey chiefly upon Snakes and Lizards in Australia; and of reptiles, besides those Snakes which prey upon other Snakes, the Monitor Lizards frequently seize and devour them.
The series of Ophidians is arranged by our most eminent herpetologist, Dr. A. Günther, into five subordinate groups, which he characterises as follows:—
I.Burrowing Snakes, living under ground, only occasionally appearing above the surface. They are distinguished by a rigid cylindrical body, short tail, narrow mouth, small head not distinct from the neck, little teeth in small number, and by theabsence or feeble development of the ventral shields. They feed chiefly on small invertebrate animals. Not any of them are venemous.
II.Ground Snakes, or species which live above ground, and only occasionally climb bushes or enter the water; their body is more or less cylindrical, very flexible in every part, and of moderate proportions. Their ventral shields are broad. They feed chiefly on terrestrial vertebrate animals. By far the greater number of Snakes belong to this category, and it is represented by many variations in all of the three sub-orders to be noticed presently.
III.Tree Snakes, or species passing the greater part of their life on bushes and trees, which they traverse with the utmost facility. They are distinguished either by an exceedingly slender body, with broad, sometimes carinated, ventral shields, or by a prehensile tail. Many of the species are characterised by their vivid coloration, of which green forms the principal part. We shall see, in the sequel, that the first and third sub-orders offer numerous instances of Tree Snakes; the Tree Snakes of the second sub-order being confined to Tropical Africa. They feed on animals which have a mode of life similar to their own; only a few species on eggs.
IV.Fresh-water Snakes, distinguished by the position of the nostrils, which are placed on the top of the snout, and by a tapering tail. They inhabit fresh-waters, and are, therefore, excellent swimmers and divers; only a few species (which also in external characters approach the following group, that of the true Sea Snakes) venture out to sea. They feed on fishes, frogs, crustaceans, and other water animals, and are viviparous. Not any of them are venemous.
V.Sea Snakes, distinguished by a strongly compressed tail, and by the position of the nostrils, which are placed as in the last group. They live in the sea, only occasionally approaching the land, feed on marine fishes, are viviparous and venemous. One genus only (Platurus) has the ventral shields so much developed as to be able to move on land. No Oceanic Serpent is known of gigantic dimensions, such as is currently alleged to have been seen by unscientific observers.
"Although these five groups," remarks Dr. Günther, "are not separated from each other by defined lines of demarcation, and frequently pass into one another by intermediate forms, yet a family and genus which should be composed of species of several of these groups would be a very unnatural assemblage of heterogeneous forms."
It is also remarked by the same naturalist that there is no sharp boundary line between the order of Snakes and that of Lizards. There are various limbless Saurians of Ophidian appearance, but the systematic position of which is decided by the structure of their jaws. The Common Orvet, or Slow-worm, is a familiar instance. On the other hand, certain Ophidians remind us, by several characters, of the Saurian type,—as the Snakes constituting the familiesTyphlopidæ,Tortricidæ,Xenopeltidæ, andUropeltidæ, which are distinguished by polished, closely adherent, rounded, sub-equal scales, much resembling the smooth scales of various Scincoid Lizards; most of them have a very narrow mouth, unlike the enormous gape of the typical Serpents, and some are without that longitudinal fold in the median line of the chin which is so characteristic of most Ophidians; moreover, most of them have rudiments of the bones of a pelvic arch. "The reason," alleges Dr. Günther, "why we adopt the view of those systematists who refer such reptiles to the Ophidians, instead of associating them with the limbless Scincoid Lizards, is the loose connection of the jaw-bones, a character which must be considered as peculiar to the Ophidians, and which is only somewhat less developed in the families mentioned than in the typical forms. The two halves of the lower jaw in Ophidians, namely, are not united by a bony symphysis, but by an elastic ligament. The peculiar mobility of the jaw bones enables the Snakes to extend the gape in an extraordinary degree, and to work their prey down through the collapsed pharynx."
The same naturalist classifies theOphidiainto three sub-orders, in which the venemous Snakes are separated from the others; but to some herpetologists this arrangement must appear rather forced, as hisVenemous Colubrine Snakeshave certainly a much nearer resemblance in other respects to theColubridæthan they have to theViperine Snakes. For the most part, these reptiles are providedwith numerous teeth, which are lengthened, conical, thin and pointed like a needle, and more or less bent backwards.
In Dr. Günther'sfirst sub-order, that ofNon-venemous Snakes, the teeth are either entirely smooth, or only the last of the maxillary series is provided with a faint longitudinal groove, which is not intended to convey a virus into the wound, the groove appearing rather to increase the strength of the tooth. Many of them have long teeth in front of the jaws or of the palate, but these are never grooved or perforated, and only serve to afford a firmer hold on the living and struggling prey.
"The structure of the venom-tooth is not the same in all poisonous Snakes: in some it is fixed to the maxillary bone, which is as long or nearly as long as in the non-venemous Snakes, and generally bears one or more ordinary teeth on its hinder portion. The venom-tooth is fixed more or less erect, not very long, and its channel is generally visible as an external groove. The poisonous Snakes with such a dentition have externally a more or less striking resemblance to the non-venemous Serpents, and on this account they are designated asVenemous Colubrine Snakes, forming oursecond sub-order." Two very distinct families are here brought together—viz. theElapidæ(which comprises the Cobras and many others), and theHydrophidæ(or Sea Snakes).
"In the other venemous Snakes, composing thethird sub-order, the maxillary bone is extremely short, and does not bear any teeth except an exceedingly long fang, with a perfectly closed externally invisible channel in its interior. Although this tooth also is fixed to the bone, the bone itself is very mobile, so that the tooth, which is laid backwards when at rest, can be erected the moment the animal prepares to strike. This tooth or fang, like all the other teeth, is not only occasionally lost, but appears to be shed at regular intervals. From two to four other venom-fangs in different stages of development, destined to replace the one in action, exist between the folds of the gum, and are not anchylosed to the bone." The more characteristic venemous Snakes appertain to this sub-order—viz. the two familiesCrotalidæ(comprehending the Rattlesnakes, the Fer-de-lance, &c.) andViperidæ(comprising the Vipers, Puff-adders, &c.).
Let it be particularly borne in mind that the supposed distinguishingcharacters of all poisonous Snakes, as assigned by sundry mischievously ignorant writers, are those of the third of the foregoing sub-orders almost exclusively. Even the broad, flat, and lanceolate form of head is exemplified in certain Tree Snakes of the non-venemous genusDipsas, and not in the Cobras and others that are quite as deadly—e.g.Hoplocephalus,Bungarus,Naja,Elaps, and others constituting the Colubriform familyElapidæ.
These are distributed by Dr. Günther under numerous families, of which we can only notice the more prominent, and some of the more conspicuous species, in a popular exposition.
TheTyphlopidæ, or Blind Snakes, comprise forms which are the most remote from the true Ophidian type. They live under ground, their rigid body and short curved tail being adapted for burrowing. After showers of rain they occasionally appear above ground, and then they are tolerably agile in their serpentine movements. The eye, which is scarcely visible in many species, can give to them only a general perception of light. They feed on worms and small insects, the tongue being forked, and, as in other Snakes, frequently exserted. They are oviparous. The smallest species of Snakes belong to this family, some of them being only half the size of a common earth-worm, to which they bear a superficial resemblance. Such, indeed, are the small vermiform Snakes already referred to, as being foolishly considered venemous by most natives of India. Species of this family inhabit almost every country within and near the tropics.
TheTortricidæare akin to theTyphlopidæ, and have rudiments of hind limbs hidden in a small groove on each side of the vent, also a longitudinal fold at the chin. The "Coral Snake" of Demarara (Tortrix scytale) appertains to this family; and the genusCylindrophis, different species of which inhabit the great Asiatic archipelago, with the island of Ceylon.
The familyXenopeltidæconsists of a single species only, so far as hitherto known, theXenopeltis unicolor, which is common in the Indo-Chinese and Malayan countries. It grows to three or four feet in length, and when alive is uniformly steel-blue,most beautifully iridescent, beneath white; but the blue fades to brown after long immersion in spirits. Young examples have a white collar. Mr. W. Theobald remarks of it that "this Snake is common in Lower Pegu and the Tenasserim provinces, and is very malignly beautiful, though of repulsive physiognomy. The skin is loose and thick, and its habits are nocturnal. The following illustrates its ferocious nature:—I once remarked a Colubrine Snake (Ptyas mucosa), some five feet in length, in the hedge of the Circuit-house of Bassein. On running downstairs, the Snake had vanished, but on searching for it I saw its tail sticking out of a hole beneath a wooden plant-case. Do what I might I could not drag it out, as it seemed held fast within. I therefore, with some trouble, overturned the plant-case, and then saw that the unlucky Colubrine Snake was firmly pinned by a largeXenopeltis, into whose hole it had unwittingly entered. TheXenopeltisseemed about four feet in length; but, on perceiving itself uncovered, released its hold of thePtyasand made its escape." TheXenopeltispreys chiefly on small mammalia, which it hunts for in their subterranean holes; and in some respects it approximates thePythonidæ.
TheUropeltidæ, or Shield-tails, constitute a very curious family of Burrowing Snakes, which bear considerable resemblance to theTyphlopidæ, but have a very peculiar, short, strong, posteriorly shielded tail, adapted for working their way below the surface. The species are mostly small, and hitherto they have been found chiefly in Ceylon, but a few also in the peninsula of India. They are by no means scarce, but escape observation from their peculiar mode of life. Dr. Kelaart remarks that "they are timid creatures, seldom making their appearance above ground; living chiefly in ant-hills or dunghills, sometimes also several feet deep in rich loamy soil. They feed on ants, small earth-worms, and the larvæ of insects, and at least one species has been ascertained to be viviparous. Five genera and eighteen species of them are recognised."
TheCalamaridæform an extensive family of diminutive slender Snakes, from one to two feet in length, many species of which inhabit both the Old World and the New, though the same kinds are not found both East and West. They keep to the ground, beneath stones, fallen trees, &c.; and their food appears to consist chiefly of insects. They are gentle, and never attemptto bite, and themselves very commonly become the prey of the smallerElapidæ, certain of which indeed bear considerable resemblance in appearance to theCalamaridæ, but are readily distinguished by possessing the poison-fangs.
TheOligodontidæare another extensive family of small ground Snakes, which are peculiar to South-eastern Asia and its great archipelago. They conduct to the terrene genera of the great familyColubridæ.
TheColubridæare divided by Dr. Günther into ground Colubrines (Coronellinæ), true Colubrines (Colubrinæ), bush Colubrines (Dryadinæ), and fresh-water Colubrines (Natricinæ); and he remarks that "they are found in every part of the temperate and tropical regions, but are only scantily represented in Australia and in the islands of the Pacific. The species are so numerous and show such a gradual passage between extreme forms, that, although genera can be easily characterized, it is almost impossible to distinguish wider groups by definite characters." Among them theCoronellinæapproximate the immediately preceding families, and, like them, live on the ground, and are not generally of brilliant colouring, though a few species which frequent grassy plains are of a bright green colour. TheColubrinæ"form, as it were," writes Dr. Günther, "the nucleus of the whole sub-order of innocuous Snakes: they are typical forms, not characterized by the excessive development of some particular organ, but by the fairness of the proportions of all parts. Yet some of them have a more slender body than others which always live on the ground; they are land Snakes, but swim well when driven into the water, or climb when in search of food. They are of moderate or rather large size." In theDryadinæthe form is elongate and somewhat compressed, indicating their climbing propensities; they have the body not so excessively slender as in the true Tree Snakes, to which they lead off. They are much more numerous in the New World than in the Old, and their ground-colour is very commonly green. TheNatricinæare generally not very elongate or compressed, and most of them have keeled scales. They freely enter the water in pursuit of their food, which consists chiefly of frogs and fishes. All the Snakes of the preceding three sub-families overpower their prey by throwingsome coils of the body round or over it, and commence to swallow it only after it has been smothered, or at least exhausted; but theNatricinæswallow their prey immediately after they have seized it.
Of the sub-familyCoronellinæ, one species of the typical genusCoronellais widely diffused over Europe, and has only of late years been recognised as an inhabitant of the British Islands, theCoronella austriaca. Another,C. girondica, occurs in Italy. Others are found in Africa, America, and Australia. TheC. austriacahas somewhat the appearance of the common Adder, for which it is often mistaken; but it is non-venemous, though rather a fierce reptile, which bites and holds on; and as it occurs in Malta (where no venemous species is known to exist), it is doubtless the supposed Viper which seized upon the apostle Paul. Several other genera are recognised.
Of theColubrinæ,Rhinechis scalaris,Coluber æsculapii,C. quadrilineatus,Elaphis quater-radiatus, and three species ofZamenisinhabit Europe: there are five ofColuberin North America, and the well-known "Black Snake" of the Anglo-Americans is theCoryphodon constrictor. Other species ofCoryphodonorPtyasinhabit South-eastern Asia, as the different "Rat Snakes" of Anglo-Indians, of whichPtyas mucosusis particularly common in India, where it is encouraged by reasonable people as a destroyer of the far more troublesome Brown Rat (Mus decumanus).
TheDryadinæare chiefly American, and do not call for particular further remark; but theNatricinæare very numerous, and there are three species in Europe of its most prominent genus,Tropidonotus—viz.T. natrix,T. hydrus, andT. viperinus. [Dr. Günther gives as many as twenty-one species of this genus as inhabitants of the Indian region alone, and there is reason to believe that that number is far from being complete. Others inhabit North America and North-western Australia, and some generic groups have been detached that are not very conspicuously separable.]