Yet they can often remain for a long time both under water and under ground, for they are still cold-blooded animals, breathing very slowly, and easily falling into a state of torpor when the air around them is cold and chill. They are but the first step, as it were, to active land-animals; yet they have played a great part in the world, and when we know their history we shall be surprised to find how much Life has been able to make of her cold-blooded children.

To learn how this has been, however, we must travel away from home and our own surroundings. The tiny brown lizard which runs over our heaths, while its legless relation, the slowworm, burrows in the ground,—the few snakes which glide through the grass of our meadows, and the stray turtles thrown at rare intervals on our shores,—tell us very little about true reptile life. It is to Africa, India, South America, and other warm countries, that we must go to find the formidable crocodiles, huge tortoises, large monitor-lizards, and dangerous boa-constrictors, cobras, and rattle-snakes. And even then, strong and powerful as some of these creatures are, they do not tell us half the history of the cold-blooded air-breathers. For the day of reptile greatness, like that of the sharks and enamel-scaled fish, was long long ago.

Now that we know how frogs pass from water-breathing to air-breathing, and how axolotls, accustomed to live all their life in the water, can lose their gills and become land-animals, we can form an idea how in those ancient days, while still the huge-plated newts were wandering in the marshes, some creatures which had lost their gills would take to the land, and their young ones starting at once as air-breathers, as the black salamanders do now (see p. 80), would in time lose all traces of the double or amphibian  life, and become true air-breathing reptiles.

At any rate, there we find them appearing soon after the coal-forest period passed away, at first few and far between, in company with the large amphibians, but spreading more and more as the ages passed on, till they in their turn became monarchs of the globe. Already, when the coal-forests had but just passed away, a lizard, in some points like the monitors that now wander on the banks of the Nile, was living among his humbler neighbours; and from that time onwards we find more and more reptiles, till just before the time when our white chalk was being formed by the tiny slime-animals at the bottom of the sea, we should have seen strange sights if we could have been upon the globe. For the great eft was no longer

All over the world, and even in our own little England, which was then part of a great continent, cold-blooded reptiles of all sizes, from lizards a few inches long to monsters measuring fifty or sixty feet from head to tail, swarmed upon the land, in the water, and in the air. There were among them few kinds something like our tortoises, lizards, and crocodiles; but the greater number were forms which have quite died out since birds and beasts have spread over the earth, and a wonderful and powerful set they were.

Some were vegetable-feeders, which browsed upon the trees or fed upon the water-weeds, as our elephants and giraffes, our hippopotamuses and sea-cows do now. Others were ferocious animal-eaters, and their large pointed teeth made havoc among their reptile companions, as lions and tigers do among beasts. Some swam in the water devouring the fish, while others, like birds or bats, soared in the air.

In the open ocean were the sea-lizards, some called Fish-Lizards, like huge porpoises thirty feet long, but really cold-blooded reptiles, with paddles for legs, and long flattened tails for swimming. Woe to the heavily-enamel-scaled fish when these monsters came along, their pointed teeth hanging in their widely-gaping mouths as they raised their huge heads, with large open eyes, out of the water! Then among these were others with long swan-like necks and small heads, which would strike at the fish below them in the water, while other slender, long-bodied monsters, measuring more than seventy feet from tip to tail, flapped along the sea-shore with their four large paddles, or swam out to sea like veritable sea-serpents, devouring all that came in their way. These were all water-reptiles, while there were also many smaller land-lizards playing about upon the shore, and among the trees and bushes. But the strangest of all were perhaps the "Flying reptiles" of all sizes, from one as small as a sparrow to one which measured twenty-five feet from tip to tip of its wings. These reptiles did not fly like birds, for they had no feathers, but only a broad membrane, stretching from the fifth finger of their front claw to their body, and with this they must have flown much as bats do now, while some of them were armed not only with claws, but also with hooked beaks and sharp teeth, with which they could tear their prey.

And meanwhile upon the land were wandering huge creatures, larger than any animal now living, which were true reptiles with teeth in their mouths, yet they walked on their hind legs like birds, probably only touching the ground with their short front feet from time to time, as kangaroos do. They had strong feet with claws, the marks of which they have left in the ground over which they wandered, supporting themselves by their powerful tails as they went.

Some of them were peaceful vegetarians, browsing on the tree-ferns and palms, and rearing their huge bodies to tear the leaves from the tall pine-trees. But others were fierce animal-feeders. Fancy a monster thirty feet high, with a head four or five feet long, and a mouth armed with sabre-like teeth, standing upon its hind legs and attacking other creatures smaller than itself, or preying upon those other huge reptiles which were feeding peacefully among the trees. Surely a battle between a lion and an elephant now would count as nothing compared to the reptile-fights which must have taken place on those vast American lands of the west, or on the European pasture-grounds, where now the remains of these monsters are found.

But where are they all gone? We know that they have lived, for we can put together the huge joints of their backbones, restore their gigantic limbs, and measure their formidable teeth, but they themselves have vanished like a dream. As time went on, other and more modern forms, the ancestors of our tortoises, lizards, crocodiles, and afterwards snakes, began to take the place of these gigantic types; while warm-blooded animals, birds and beasts, began to increase upon the earth. Whether it was that food became scarce for these enormous reptiles, or whether the birds and beasts drove them from their haunts, we are not yet able to find out. At any rate they disappeared, as the ancient enamelled fishes and large newts had disappeared before them, and soon after the beds of white chalk were formed, which now border the south of England and north of France, only the four divisions of tortoises, lizards, crocodiles, and snakes, survived as remnants of the great army of reptiles which once covered the earth.

Ah! if we could only have a whole book upon reptiles to show how strangely different these four remaining groups have become during the long ages that they have been using different means of defence; and how, even in a single group, they employ so many varied stratagems to survive in the battle of life! Look at the tortoises with their hard impregnable shells, the crocodiles with their sharp-pointed teeth and tough armour-plated skins, and the silently-gliding snakes with their poisonous fangs or powerful crushing coils. See how the tiny-scaled lizard darts out upon an insect and is gone in the twinkling of an eye, and then watch the solemn chammleon trusting to his dusky colour for protection, and scarcely putting one foot before another in the space of a minute.

Each of these has his own special device for escaping the dangers of life and attacking other animals, and yet we shall find, before we finish this chapter, that they are all formed on one plan, and that it is in adapting themselves to their different positions in life that they have become so unlike each other.

We shall all allow that the Tortoises are the most singular of any, and it is curious that they are also in many ways the nearest to the frogs and newts, although they are true reptiles. Slow ponderous creatures, with hard bony heads (Fig. 20), wide-open expressionless eyes, horny beaks, and thick clumsy legs, the tortoises seem at first sight to be only half alive, as they lumber along,

carrying their heavy shell, and eating, when they do eat, in a dull listless kind of way. They do, in truth, live very feebly, for they can only fill their lungs with air by taking it in at the nostrils and swallowing it as frogs do, and then letting it drift out again as the lungs collapse, for their hard shell prevents them from pumping it in and out by the movement of their ribs like other reptiles. This slowness of breathing and the fact that they have only three-chambered hearts like frogs (see p. 76), so that the good and bad blood mix at every round, causes them to be very inactive, and they digest their food very slowly, and have been known to live months and even years without eating.

This sluggishness would, indeed, certainly be their ruin in a bustling greedy world, if it were not for the strong box in which they live. Take in your hand one of the small Greek or American tortoises, so often sold as pets, and you will see how well he can draw back out of harm's way, while at the same time you will, I think, be sorely puzzled to understand how he is made. His head, his four legs, and his tail, with their thick scaly skin, are intelligible enough. But why do all these grow on to the inside of his shell, so that when you trace them up you cannot find the rest of his soft body? You would hardly guess that his shell is  the rest of his body, or at least of his skeleton. But it is so. The arched dome which covers his back is made of his backbone and ribs, and the shelly plates arranged over it are his skin hardened into horny shields, which, in the Hawksbill turtle, form the tortoise-shell which is peeled off for our use; while the flat shell under his body is the hardened skin of his belly, and the bones which belong to it.

Let us make this clear, for it is a strange history. If you look at the skeleton of a lizard (Fig. 23, p. 103), it is all straight-forward enough. His head fits on to his long-jointed backbone, which is able to bend in all parts freely, down to the very tip of his tail. His front legs with their shoulder bones (s ), and his hind legs with their hip bones (k ), are attached in their proper places to his backbone, and lastly, his ribs (r ) protect the inside of his body, and by expanding and contracting pump the air in and out of his lungs, the front ribs being joined underneath in a breastbone. It is easy to see, therefore, that the lizard may be active and nimble, twisting his body hither and thither, and escaping his enemies by his quickness. But the tortoise is slow and sluggish, and has only managed to baffle the numberless animals which are looking out for a meal by fabricating a strong box to live in. But he had to make this out of the same kind of skeleton as the lizard, with the one difference that he has no breastbone. Let us see how it has been brought about. The bones of his neck are jointed and free enough as you can see (Fig. 21), and so are the joints of his tail, beginning from behind his hip bones (h ). But with his back it is different. The backbone can be clearly seen inside the empty shell, running from head to tail so as to cover the nerve-telegraph, but the joints (j ) have all grown together, and on the top they have become flattened into hard plates, sp  in the lizard and snake, pp. 103, III.") ?> while the ribs (r ) which are joined to them have also been flattened out and have grown firmly together so as to make an arched cover or carapace.  If now you look at the back of the young tortoise (Fig. 22), which has been taken out of the egg before it was full-grown, you will see these plates (p ) on the ", "
", "center", "70", "5", "5", "[Illustration]", "Fig. 22.
Back of a Young Tortoise.—(From Rathke. )
ts,  Tortoise-shell covering the whole carapace; this has been removed on the right side; mp,  marginal plates binding the edges of the ribs; np,  neck-plate; p,  plates formed of the top of the backbone joints which have grown together; r,  ribs which have not yet spread out so as to form a continuous shell; lm, lm',  front and hind leg muscles not yet covered by the carapace.") ?> side where the tortoise-shell (ts ) has been peeled off. They have not yet widened out enough to be joined together, and the ribs (r ) are as yet only united by strong gristle. But what is that row of oblong plates (mp ) round the edge? Those are the marginal plates, and they are mere skin bones, like the bony plates of the crocodile, but they are all firmly fixed together so as to bind the edges of the ribs, while plates of the same kind form the shell under the body, and the whole is covered by the horny skin.

But there still remains another great puzzle. How come the shoulder bones and hip bones of the tortoise to be inside his ribs instead of being outside them, as in other animals? But look again at our baby tortoise, and you will see that the muscles of his front legs (lm,  Fig. 22) are not covered by ribs, neither are those of his hind legs (lm' ). They stand just like those of other animals, in front between the ribs and the neck, and behind between the ribs and the tail. But as the tortoise grows up, the bony plates press forwards and backwards, and cover up the shoulders and hips, protecting the soft legs and neck, and giving him the curious appearance of living inside his own backbone and ribs.

In this way, then, the tortoises have managed to hold their own in the world. Living slowly, so that they sometimes go on growing up to eighty years old, wanting but little food, and escaping the cold by sleeping the winter months away in some sheltered nook, they ask but little from Life, while they escape the dangers of sluggishness by growing their skeletons so as to form a citadel which even birds and beasts of prey can rarely break through. They are, it is true, often eaten when young, and the jaguar of Brazil knows how to dig the poor American tortoise out of his shell and eat him; while large birds are formidable enemies to our Greek tortoise, and are said to drop it down on the rocks, and break it to pieces. But, on the whole; they escape most of these dangers, and wander in the woods and dry sandy places of sunny Greece and Palestine, laying their bullet-shaped eggs in warm spots to hatch, seldom wandering far from home, and lying down for their winter's sleep under heaps of drifted leaves or in holes of the ground.

These are true Land-tortoises, and so are the gigantic tortoises which used to live in the island of Aldabra, and others still surviving in the Galapagos and other islands near Madagascar, which weigh at least 200 pounds, and on whose backs Mr. Darwin rode when he found them travelling up the island to get water to drink, feeding on the juicy cactus as they went. Some carapaces in our museums belonging to these tortoises measure four feet long and three broad; yet they were timid fellows when alive, drawing back completely within their shells when danger was near. We even find some smaller land-tortoises in America, called the Box-tortoises, which have soft joints in their under shell, so that they can draw it up both in front and behind, shutting themselves completely in.

Not so the River-tortoises, which are greedy animal-feeders, and as they live in the water do not need the same protection. Their box is much flatter and more open at the ends, so as to allow them to swim freely with their webbed feet; and they arc fierce and bold, the Snapping Turtle of the lakes and rivers of America being a terrible fellow, tearing the frogs and fishes in the water with his sharp claws, and even snapping strong sticks in half with his powerful beak. The Mud-tortoises, too, which swim swiftly with their strong legs and long neck outstretched, do not need a hard shell, and they have scarcely any plate below, and only a gristly leathery covering above, which looks very like the mud in which they hide.

Lastly the Sea-tortoises or Turtles, which swim in the warm parts of the Atlantic and Pacific Oceans, have only an open flat shell under which they cannot draw their head and feet, for they strike out boldly into the open ocean, feeding on sea-weed, jelly-fish, and cuttle-fish, rowing grandly along with their broad paddles which they feather like oars as they go. They have only one time of weakness—when they come on islands, such as Ascension and the Bahama Islands, which they choose probably because they find fewer large animals there. There the mother turtle arrives at night, looking fearfully around, and if all is still comes flapping in over the sand, and, clearing a hole with her flippers, lays about 200 soft round eggs and covers them up and leaves them. Then in about a month the young turtles come out and make at once for sea, though many of them fall victims to large birds of prey on their way. Woe, too, to the mother when she is laying her eggs, if these large birds are near, for she cannot defend her soft body; or, worse still, if the natives are on the look-out; for then the Green Turtle, coming ashore from the Atlantic, is tilted over on her back and killed for food; and the I Iawk's-bill Turtle from the Indian or Pacific Oceans is cruelly stripped of its shell for ornaments. Yet they must run these risks, for their eggs would not hatch without the warm sun, and we see how great is the gap between the last water-breathers and the first air-breathers, when we remember that the frogs go back to lay their eggs in the water, while the tortoises, even when they live far out at sea, are forced to come in to shore, in spite of great dangers, to lay their eggs that their little ones may begin life upon land.

And now, if we leave the tortoises and turn to the Lizards, we find them meeting life's difficulties in quite a different way. Here are no sluggish movements, horny beaks, and strong boxes; but bright-eyed creatures covered with shining scales, their mouths filled with sharp teeth,with which even the small lizards can bite fiercely, and having nimble lissome bodies, which wriggle through the grass or up the trees in the twinkling of an eye. Yet the lizards, as we have seen, are formed on the same plan as the tortoise, and their scales are thickenings in their outer skin, just as his tortoise-shell is, and not true scales like those of fish. They have learned to hold their own by sharpness and quickness, and are probably the most intelligent of all the cold-blooded animals, though even they are only lively in a jerky way under the influence of warmth. They can breathe more easily than the tortoise, for their ribs rise and fall, drawing in and driving out the air they need; but they are still cold-blooded, for their heart has only three chambers. It is when the bright sun is shining that they love to dart about, chasing the insects upon which they feed; and the joints of their backbone move so easily upon each other that they can twist and turn in all imaginable ways, keeping their heads twisted in a most comical manner when on the watch for flies. Nay, the very vertebrae themselves are so loosely made that they can split in half, and if you seize a lizard by the tail he will most likely leave it in your hand and grow another.

They can live both in dry sandy places, where larger animals cannot find food and water, and in thick underwood, and marshy unhealthy places, where more quickly-breathing animals would be poisoned by the fetid air; and we find them swarming in hot countries in spite of enemies, their scales protecting them from the rough surface of the rocks and trees on which they glide, their feeble legs scarcely ever lifting their body from the object on which they glide rather than walk.

The true land-creepers, like our little Scaly Lizard, lurk in dry woody places, and on heaths and banks, darting out on the unwary insects. Many of them lay their eggs in the warm sand or earth, but the Scaly lizard carries them till they are ready to break, Iso that the young ones come out lively and active as the eggs are laid. Others have taken to the water, and e among these are the Monitors of Africa and Australia, which feed on frogs and fish and crocodiles' eggs, and are so strong and fierce that they often der the water. Some are tree and wall climbers, such as the "Geckos," with thick tongues and dull mottled skins, and they have sharp claws it and suckers under their toes, so that they can hang or walk upside down, on ceilings or overhanging rocks, or on the smooth trunks of trees; and they love to chase the insects in the hot sultry nights, tracking them to their secret haunts. They are far more active than the large gentle Iguanas or Tree-Lizards of South America, from a few inches to five feet long, which may be seen among the branches of the trees of Mexico, their beautiful scales glistening in the sun as they feed on the flowers and fruit. They swarm on all sides in those rich forest regions, scampering over the ground, and then clinging with their claws to the tree-bark as they gradually mount up into the dense foliage; and they have many advantages, for not only can they climb to great heights out of the reach of beasts of prey, but they can also swim well, having been known to fling themselves from the overhanging branches into the water below when danger was near. They do not, moreover, descend as gracefully as the "Flying Lizards" of the East Indies, which have a fold of skin stretched from the lengthened ends of their hinder ribs, so that they sail from branch to branch as they chase the butterflies and other insects.

But the most curious of all tree-lizards is the Chameleon, with his soft warty skin, his round skin-encircled eyes, his birdlike feet, and his clinging tail. He never hurries himself, but putting forward a leg, at the end of which is a foot whose claws are divided into two bundles, he very deliberately grasps the branch, as a parrot does, loosens his tail, draws himself forward, and then fastens on again with tail and claws; while his eyes, each peering out of a thick covering skin, roll round quite independently of each other, one looking steadily to the right, while the other may be making a journey to the left. What is he looking for? Just ahead of him on a twig sits a fly but he cannot reach him yet. So once more a leg comes out, and his body is drawn gradually forwards. Snap! In a moment his mouth has opened, his tubelike tongue, with clubbed and sticky tip, has darted out and struck the fly, and carried it down his throat, while the chameleon looks as if he had never moved. It is not difficult to imagine that such a slow-moving animal, whose natural colour is a brownish green like the leaves among which he moves, would often escape unseen from his enemies. And when light falls upon him, his tint changes by the movement of the colour-cells in his skin, which seem to vary according to the colour of the objects around, whenever he is awake and can see them.

So by the waterside, on the land, and among the trees, the lizard tribe still flourish in spite of higher animals; and just as we found some legless kinds among the amphibia  burrowing in the ground, so here, too, we find legless lizards, some with small scaly spikes in the place of hind legs, others, like the glass-snake of America and our English slowworm (or blindworm), which have no trace of feet outside the skin, but glide along under grass and leaves, eating slugs and other small creatures, though they are true lizards with shoulder bones and breastbones under the skin.

Here, then, we seem to be drifting along the road to snake-life, but we must halt and travel first in another direction, upwards to a higher group of animals, which may almost be called gigantic flesh-eating lizards, though they are far more formidable and highly-organised creatures. These are the Crocodiles, and no one looking at them can doubt for a moment that they at least are well armed, so as to have an easy time of it without much exertion. Huge creatures, often more than twenty feet long, with enormous heads and wide-opening mouths, holding more than thirty teeth in each jaw, they look formidable indeed as they drag their heavy bodies along the muddy banks of the Nile, their legs not being strong enough to lift them from the ground. Their whole body is covered with strong horny shields, and under these shields, on the back, are thick bony plates, which will turn even a bullet aside, and quite protect the crocodile from the fangs of wild beasts. Their eyelids are thick and strong, and they have a third skin which they can draw over the eye sideways like birds; their ears, too, have flaps to cover them, and their teeth are stronger and more perfect than any we have yet seen, for they are set in sockets, and new ones grow up inside the lower part of the old ones as they are broken or worn away.

But it is in the water that we see them in their full strength; there they swim with their webbed feet and strokes of their powerful tail, and feed upon the fishes and water animals—monarchs of all they survey. Nor is the crocodile content with mere fish-diet. Often he will lie with his nostrils just above the water and wait till some animal—it may be a goat, or a hog, or even a good-sized calf—comes to drink, then he will come up slowly towards it, seize it in his formidable jaws, or sometimes strike it with his powerful tail, and drag it under water to drown. For he himself can shut down his eyelids and the flaps over his cars, and he has a valve in the back of his throat which he can close, and prevent the water rushing down his open mouth; and after a while he rises slowly till his nostrils are just above the water, and he can breathe freely while his victim is drowning, because his nose-holes are very far back behind the valve. Then when it is dead he brings it to shore to tear it to pieces and eat it.

Thus the crocodiles of the Nile and the Ganges, the Gavials with their long narrow snouts, and the Alligators of America, with their shorter and broader heads, feed on fish and beasts, and all dead and putrid matter, acting as scavengers of the rivers; while they themselves are almost free from attack, except when tigers fall upon them on land. But it is the young crocodiles which run the most risks when they come out of the small chalky eggs which have been hatched in the warm sand of the shore. True, their mother often watches over them at this time, and even feeds them from her own mouth; but in spite of her care many of them are eaten in their youth by the tortoises and fishes which they would themselves have devoured by-and-by, if they had lived to grow up; while the monitors, ichneumons, waterfowl, and even monkeys, devour large numbers of crocodiles' eggs.

And now, if we were to turn our backs upon the great rivers in which these animals dwell, and wander into the Indian jungle or the South American forest, we might meet with enemies far more dangerous and deadly, although they stand much lower in the reptile world. Who would think that the huge boa of South America, and the python and poisonous cobra of India, or even our own little viper, whose bite is often death to its victim, are creatures of lower structure than the harmless little lizard or the stupid alligator? Yet so it is. For Snakes have no breastbone and have lost all vestiges of front legs and shoulder bones, nor have they any hips or hind legs except among the boas and rock-snakes; and even these have only small traces of hips, which calry some crooked bones, ending in horny or fleshy claws, in the place where hind legs ought to be. They have no eyelids (and by this we may know them from the legless lizards), but their skin grows right over the eyes, so that when a snake casts its skin there are no holes where the eyes have been, but only clear round spaces like watch-glasses, in the scaly skin. Their ears have no drum, and are quite hidden under the scales with which their body is so thickly covered that they must feel very little as they glide along. These scales, like those of the lizard, are thickened parts of the outer skin, and if you stretch a piece of snake-skin you can see them lying embedded in it, the clear skin itself showing between.

We must not, however, imagine that the snake is at a disadvantage because he has lost so many parts which other reptiles possess. On the contrary, he has most probably lost them because he can do better without them. The transparent tough skin over his eye is a far better protection in narrow rugged places, and among brakes and brambles, than a soft movable eyelid; and if he does not see as well as the crocodile, he has a most delicate organ of touch in his long, narrow, forked tongue, with which he is constantly feeling as he goes, touching now on one side, now on the other, each object he comes near, and drawing the tongue in at every moment to moisten it in a sheath at the back of his throat. A breast bone, moreover, would have been a decided hindrance to him, for he wants the free use of all his ribs; and as to the loss of his legs—in the place of four he has often more than two hundred. For all along his backbone, except just at the head and tail, a pair of ribs grow from each vertebra, being joined to it by a cup-and-ball joint (c  and b,  Fig. 26), and the muscles between them are so elastic that the ribs can be drawn out so that the body seems to swell, and then drawn back towards the tail. In doing this they strike the ground and the snake moves forwards, just as a centipede does on its hundred legs.

It is worth while to take our harmless Ringed Snake in your hand to feel this curious movement to and fro of the ribs, and to notice how the creature forces itself through your grasp. Moreover, you will learn at the same time one use of the broad single plates under the snake's body (see Fig. 27), for they, like all the scales, are loose from the skin on the side towards the tail; and as they are fastened by muscles to the ends of the ribs, you will find that at each movement they stand up a little like tilts on a roof, and their edges coming against your hand help to drive the snake forward.

Another thing you will learn if the snake does not know you, and that is how strangely they hiss, often with their mouth closed, while their whole body seems to quiver. This is very puzzling at first, till you learn that one of their lungs has shrunk up, and the other is a very long and narrow bag stretching nearly the whole length of the snake's stomach, and the hissing sound is made by drawing in and forcing out the air from this long bag.

Meanwhile, another way in which the snake will escape from your hold unless you grasp it tightly, is by wriggling in all directions, so that you do not know where to expect it next; for the whole of the joints of its backbone are joined by a succession of cups-andballs, the ball of one joint fitting into the cup in the one behind it. It is easy to see how such joints can move almost every way, since the ball can twist freely in the cup wherever the muscles pull it (except where checked by the spines on the top of the backbone), and can even turn so much to one side that the snake can coil itself round or tie itself into a knot.

A creature that can glide along so smoothly, twist about so freely round trees, through narrow openings and tangled brushwood, and even swim in the water, has no small advantage in life; and the snake can also coil itself up under a heap of dead leaves or in a hollow trunk of a tree for safety, or to watch for its prey when no animal would suspect it was near. But even the harmless snakes have something besides this, namely, the power of swallowing animals much' broader and. thicker than themselves. You will see on looking at the lizard's skull (p. 103) that its bottom jaw is not joined at once to the top one, but there is a bone (q ) between, which enables it to open its mouth wider than if the two jaws touched each other. Now this bone (q ) in the snake's jaw is so loosely hung that it moves very easily, and the lower jaw also stretches back far behind the upper one, so that when the snake brings the jaw forward it can open its mouth enormously wide. Nor is this all; it can actually stretch the bones of its jaws apart, for they have not their pieces all firmly fixed together. In the front of the mouth each jaw has elastic gristle in the place of bone, and the two halves of the jaw can thus be forced apart from each other, making room for a very large mouthful indeed.

Now the snake's teeth are all curved towards the back of his mouth, and they are never used for chewing or tearing, but only for holding and packing down its food. So when he seizes a creature too large to be easily swallowed, he fastens his front teeth into it and then brings forward one  side of his jaws. He then fixes the teeth of this side into the animal, and holds it fast while he brings forward the jaws on the other  side, fixes these teeth, then loosens and brings forward the others, and so on. In this way he keeps his mouth stretched over the prey and gradually forces it down his elastic throat, moistening it well all the time with slime from two glands, one on each side of his mouth, and when it is swallowed he lies down and rests while the stomach digests its heavy load.

We see, then, that even harmless snakes have many advantages. Thus our ringed snake, feeding on mice and lizards, frogs and fish, wanders through the grass and bushes of warm sunny banks, feeling this side and that with his delicate forked tongue, and gliding so fast that the lizards and mice try in vain to escape; while in the water he seizes the frogs by their hind legs and jerks them into his mouth. He does not even always stop to kill his food, for a live frog has been known to jump out of a snake's mouth as it yawned after its meal. So he lives through the summer, changing his skin several times by loosening it first at the lips, so that two flaps lie back over the head and neck, and then rubbing himself through moss, bush, or bramble, so that the skin is drawn off inside out like a glove, and the new skin appears underneath, fresh, hard, and bright, ready for use. Then in the warm season the mother lays her ten or twenty soft eggs in a mass of slime, and leaves them in some sunny spot, or under a heap of warm manure to hatch, and she herself wanders away, and when winter comes coils herself up in the trunk of some hollow tree, or under the hedge, to sleep till spring comes round again. Life does not always, however, flow so smoothly as this, for the snakes have their enemies; the fox and the hedgehog love to feed upon them, the buzzard and other birds of prey swoop down upon them from above, and the weasels attack them below; and this, perhaps, is partly the reason why the ringed snake generally keeps near the water, into which it can glide when danger threatens.

All snakes are not, however, so harmless as our little ringed snake. The Pythons of India and the I3oas of America, though they have no poison in their teeth, can work terrible mischief with their powerful joints as they coil round even good-sized animals, such as an antelope or a wild boar, and crush them in their folds. Then it may be seen what a terrible weapon this flexible backbone is, as the muscles draw it tighter and tighter round the unfortunate animal, breaking its bones in pieces, till, when it is soft enough to be swallowed, the snake gradually forces it down its capacious mouth, moistening it with saliva as it goes. These large boas and pythons would, in fact, probably devastate whole countries if it were not that when they are young they arc devoured by other animals, so that very few live to grow into dangerous marauders.

Other snakes have taken a still more terrible way of killing their prey. There may be some chance of escape from a coiling snake, unless he already holds you with his teeth, but the poisonous Cobra may strike before you know that you have startled him, and though the Rattlesnake makes a sharp noise as he shakes the loose horny plates to call his mate or to alarm an enemy, yet when he means to strike his prey it is too late when the sound is heard to get out of reach of his fatal fangs. From the snake's point of view, however, it is clearly an advantage to be able with one single stroke to paralyse its prey, so that it has only to wait for the poison to do its work, and then its meal is ready. Even our little viper (see p. 121), needs only to strike a mouse once, and then draws back as the poor victim springs up and falls and dies, soon to be packed down its destroyer's throat.

Yet this terrible poison, which acts so speedily, is no special gift to the snake. It has only lately been discovered by M. Gautier that we, and probably all animals, have in our saliva some of the very poison with which the cobra kills its prey, only with us it is extremely diluted, and is useful in digesting our food. The cobra, however, has the poison, which no doubt exists in the slimy saliva of all snakes, specially concentrated and collected in two glands, one on each side of its jaw. From each of these glands (g ) a small canal passes under the eye to the edge of the jaw (c ), and opens immediately above a large curved fang (f ). This fang is fastened to a bone in the cheek which moves easily, so that the poison teeth can be shut back and lie close against the gum when they are not wanted, and when they are wanted can be brought quickly down again. Though the fang looks round like ordinary teeth, it is really flattened out like a knife-blade, and then the edges are curved forwards so as to form a groove or, in some snakes, a closed tube, down which the poison can run to the point.

Now when the snake wishes to strike its prey it raises its head, brings down the fangs and drives them into the creature's flesh, and at the same time certain muscles press upon the poison gland, so that the liquid poison is forced into the wounds. If, however, the fang was fixed to the canal, the snake's weapon would be gone if the point were broken, so we find that the canal-opening lies just above  the tube of the tooth, and behind are six small reserve teeth, covered by a tender sheath skin, ready to grow up and take its place when wanted.

Should we not think that with such weapons as these the poisonous snakes would conquer every enemy? Yet they, too, only have their fair chance of life, for besides the destruction of their eggs other dangers await them. The rapacious birds, with their feathery covering, their horny and scale-covered legs and feet, and their hard beaks, will offer battle even to a poisonous snake. The buzzard makes short work of our common viper or adder, whose fangs, though fatal to small animals, are not nearly so powerful as those of snakes of hot countries. Seizing the viper with his claws in the middle of its body, the buzzard takes no notice of its frantic struggles as, winding itself about his feet, and striking wildly at his breast, his wings, and his scaly legs, it

Keeping his own head well back out of danger, the bird lets the snake exhaust itself, waiting only till he can give a fatal blow with his beak upon its upraised head, and then, soon despatching it, tears it to pieces for a meal. Nor is even the dreaded Cobra safe from danger, for he finds his match in the powerful Adjutant birds (see p. 128), and in the Indian Ichneumon or Mungoos, which attacks the snake boldly, skilfully dodging the fatal stroke until it has broken the neck of its enemy; while in Africa the bold Secretary bird is complete master of the dreaded poisonous snakes of that country. In fact, there is little doubt that every kind of snake, either in youth or age, falls a victim to some kind of bird or beast; and even the poisonous sea-snakes, which swarm in the tropical seas, probably find their masters in the pugnacious saw-fish and the thick-skinned shark.

We see, then, that it is not without some struggle that these cold-blooded reptiles have held their own in the world, nor is it to be wondered at that only these four types—tortoises, lizards, crocodiles, and snakes—should have managed to find room to live among the myriads of warm-blooded animals which have filled the earth. These four groups have made a good fight of it, and many of them even make use of warm-blooded animals as food. The tortoises, it is true, feed upon plants, except those that live in the fresh water, and feed chiefly on fish, snakes, and frogs, while most of the lizards are insect-feeders. But the crocodile, as he lurks near the river's edge, and the snake, when he fastens his glittering eye on a mouse or bird, are both on the look-out for animals higher in the world than themselves.

It is, perhaps, natural that we should shrink from cold-blooded creatures, especially as they seem  to show very little affection. Yet lizards, tortoises, and snakes can all be made to know and care for those who are kind to them; while, as we have seen, the fierce crocodile watches over and feeds her young, and the python coils herself over her eggs, and will take no food till they arc hatched. Moreover, we can scarcely look at the quaint shell-covered tortoise, or examine the heavily-mailed coat of the alligator, or the poison-fangs of the snake, without admiring the curious devices by which these animals have managed to survive in a world which once belonged to their ancestors, before our present swarm of warm-blooded animals multiplied and took possession of their kingdom.