Yet still the great backboned division is not exhausted; on the contrary, the most powerful if not the most numerous group is still to come; that group which contains the kangaroos and opossums, the dreamy sloths, the night-loving moles and hedgehogs, the gentle lemurs and the chattering monkeys, the whales, seals, and walruses for the water; the herds of wild cattle and antelopes, of noble elephants and fleet horses, for the forests, mountains, and plains; and the ferocious beasts of prey, which make these gentler animals their food; while last, but not least, comes man himself, the master and conqueror of all.

Where, then, shall we look for the beginning of this vast multitude of warm-blooded, hairy, and four-limbed animals? If we turn back to the past, we get but little help; for though in that early time, when huge reptiles overran the world and swam in the waters, we find small animals (see Fig. 48), probably of the marsupial or pouched family, living in the forests, yet even if these were the earliest of their race, which is not at all likely, they would tell us very little about the beginning of the milk-givers, since only their lower jaws remain, and we can only guess at their relationship by these having that peculiar inward bend which we still find in all pouched animals.

No! for the few scattered facts about the lowest mammalia  or milk-giving animals we must inquire of our own day, to learn something as to the causes of their success in life. And first let us notice two important changes which give them an advantage over other backboned creatures. We have seen that, as we have gradually risen in the scale of Life, parents have taken more and more care of their eggs and their young ones. Among the boneless animals which we studied in Life and her Children,  it was not (with very few exceptions) till we reached the clever, industrious, intelligent insects, that we found them taking any thought for the weak and helpless infants. There we did find it, for insects in their own peculiar line stand very high among animals; when, however, we turned back again to begin with the first feeble representatives of the backboned family, we found the fish casting their eggs to the bottom of the sea, or on the pebbly gravel of a flowing stream, and, as a rule, taking no more thought of them. The tiny stickleback with his nest, and the lumpsucker watching over his young ones, were quite exceptions among the finny tribe. So it was again with the frogs, so with the reptiles (the turtles, lizards, and snakes), whose eggs, even when carefully buried by the mother, are often devoured by thousands before the little ones have a chance of creeping out of the shell. But when we come to the birds, there, as with the insects, we find parental care beginning—the nest, the home, the feeding, the education in flying, in singing, in seeking food, the warm-hearted love which will risk death sooner than forsake the little ones.

Yet still these same little ones have many perils to run even before they break through the shell. In spite of their parents' care, more eggs probably are eaten by snakes or weasels, field-rats, and other creatures, than remain to be hatched; while, even if they escape being devoured, the eggs must not be allowed to grow cold; and should the parents be too long away or be scared off the nest by some enemy, or should a damp cold season spoil the warm dry home, the young bird is killed in the egg before it has ever seen the light.

It is not difficult to see, therefore, that if the mother could carry the egg about with her till the little bird was born, as we found our little common lizard doing (see p. 105), it would be much safer than when left in the nest exposed to so many dangers.

Now something of this kind takes place with all that great group of animals we are going to study. The cat and the cow, as we all know, do not lay eggs as birds do; but the mother carries the young within her body while they are going through all the changes which the chicken goes through in the egg. Thus they go wherever she goes, the food which she takes feeds them, and they lie hidden, safe from danger, till they are born, perfectly formed, into the world. Nor is this all; for when at last her little ones see the light, the mother has nourishment ready for them; part of the food which she herself eats is turned into milk, and secreted by special glands, so that the newly-born calf or kitten is suckled at its mother's breast till it has strength to feed itself.

These two advantages, then,—namely, that the young have no dangerous egg-stage, but are sheltered by their mother till they are perfect, and that their mother has milk to give them for food,—at once divide the Mammalia  or milk-giving group of animals from the rest of the backboned family.

But how will this help us to learn where that great group begins? Is it possible that such creatures as these can have anything in common with reptiles and birds? To answer these questions we must travel to a part of the world which has long been separated from the great continents of Europe, Asia, Africa, and America, and where the low and feeble milk-giving animals had a chance of still keeping a place in the world.

Take a map and look at Australia, New Guinea, and Tasmania, and you will see that they are separated by a number of scattered islands from the great continents, which are not only large in themselves, but are all nearly joined together, with only narrow straits dividing them. Moreover, Australasia stands even more alone than appears at first sight; for Mr. Wallace has pointed out that a very deep sea separates New Guinea and Australia on the one hand from Borneo and China on the other; so that the land might rise several thousand feet, and yet the Australasian islands would not be joined to the great continents.

Now, if the milk-givers once had feeble beginnings, and gradually branched out, as the ages went on, into all the many forms now living, it is clear that on the great battlefield of Europe, Asia, Africa, and America, the first poor weak forms would gradually be destroyed by the stronger ones that overran these great continents. They would be crushed out, as so many of the reptiles and newts and fishes had been before them; and only their bones, if any remained, would tell us that they had once lived. But if some of them could find a refuge in a domain of their own, where after a time they had a good open sea between them and their stronger neighbours, they might have a chance of living on and keeping up the old traditions.

And this is just what we have reason to believe has been their history; for it is exactly in Australasia that we find that curious group of pouched animals, the kangaroos and other Marsupials,  Marsupium,  a pouch.") ?> as they are called, which are different from all the other milk-giving animals in the world, except the opossums of America, whom we shall speak of by-and-by.

And together with these marsupials we also find the simplest milk-giving animals now living. Come with me in imagination to a quiet creek in one of the rivers of East Australia. It is a bright summer day, and the lovely acacias are hanging out their golden blossoms in striking contrast to the tall graceful gum-trees and dark swamp oaks in the plain beyond. Come quietly, and do not brush the reeds growing thickly on the bank; for the least noise will startle the creature we are in search of, and he will dive far out of sight. There he is, gently paddling along among the water plants. His dark furry body, about a foot and a half long, with a short broad tail at the end, makes him look at first like a small beaver. But why, then, has he a flat duck's bill on the tip of his nose, with a soft fold or flap of flesh round it, with which he seems to feel as he goes? Again, he has four paws, with which he is paddling along; but though these paws have true claws to them, they have also a thick web under the toes, stretching, in the front feet (C Fig. 50), far beyond the claws, yet loose from them, so that while it serves for swimming it can be pushed back when the animal is digging in the ground. His hind feet have a much shorter web, and a sharp spur behind, like that of a game cock.

And now, as this animal turns his head from side to side you can see his sharp little eyes, but not his ears, for they are small holes which he can close quite tightly as he works along in the water, pushing his bill into the mud of the bank, just as a duck does, and drawing it back with the same peculiar jerky snap; for he too has ridges in his beak like the duck family, through which he sifts his food; while, at the same time, he has in his mouth eight horny mouth-plates, peculiar to himself.

What, then, is this four-footed animal with a beaver's fur and tail, and teeth in his mouth, and yet with a duck's bill and webbed feet? He is the lowest and simplest milk-giving animal we know of in the world—the duck-billed Platypus or Ornithorhynchus, called by the settlers the Water-mole.

If we could search along the bank we should find, somewhere below the water's edge, a hole, and again, a few feet back on the land, another among the grass and reeds; and both of these lead into a long passage, which ends in a snug underground nest—a dark hole lined with dry grass and weeds—where in the summer time (about December) we should find the mother platypus, with two or four tiny naked young ones, not two inches long, cuddled under her. How these little ones begin life we do not know. The natives talk about finding soft eggs like those of reptiles; but it seems more likely that these eggs bb break just as they are laid, like those of our common lizard (see p. 105), and the naked little ones come out alive into the nest.

And how are they fed? Their mother has no teat, like the cow, to put into their mouth, for she is a very primitive creature; only in one spot amid her fur are a number of little holes, and from these she can force out milk for them to drink as they press against her with their soft flat bills. So here, in a dark underground nest, away from the world, because she cannot, like the higher animals, carry her little ones till they are perfect, the duck-billed platypus, which may well be called "paradoxical" (see Fig. 49), enables us to picture to ourselves how, in ages long gone by, mothers first began to feed their little ones with their own milk.

And now, perhaps, you will be struck by this animal's likeness to a bird, especially when you hear that the little baby water-moles have a soft horny knob on their nose, just where young birds have a hard knob for breaking through the shell; and you will ask if milk-giving animals came from birds. Not at all; young tortoises, too, have such a knob, and so have crocodiles; and, moreover, these duck-billed moles have many parts of their skeleton, especially the shoulder bone and the separate bones of the skull, very like our living reptiles, and still more like some which lived in ages long gone by. And yet at the same time they differ essentially both from reptiles and birds in many points besides those we have been able to mention, and in one in particular, which we can understand now we have studied these groups, namely, that the platypus, like all milk-giving animals, is without that curious quadrate bore  (q,  Figs. 23 and 33) which we find in all reptiles and birds. 

Now, notice the frog, which is an amphibian and therefore lower than the reptiles, has not got this quadrate bone, though his companions the newts have; and he seems to tell us that among those old amphibians which roamed in the coal-forests of ages past, there must have been some which,—while they had that great mass of cartilage which imperfect, unborn, milk-giving animals have even now, out of part of which this bone is formed,—yet never went so far as to have the bone itself. If this is so, then here at last, in the distant past—so remote that we cannot even guess how long ago it may have been—we have a point from which the earliest ancestors of the milk-giving animals may have gone off in one direction, and those of reptiles and birds in another. And this would explain how it is that they have so many points in common, while yet the mammalia are without that special bone and other characters which are found both in reptiles and birds.

Be this as it may, here is our lowest mammalian form, and he has a relation, the Echidna, very like him in many respects, but who has made a decided step forward; for on the sandy shores and in the rocky gorges of Australia, creatures about a foot long, covered with prickly spines like hedgehogs, and called by the settlers "Porcupine Ant-eaters" (see Fig. 49), shuffle along in the twilight, thrusting out their long thin tongues from the small mouth at the end of their beak-like snout, and feeding on ants and ants' eggs. These do not belong, however, to the real ant-eater family, but are near relations to the platypus; and they are well protected by their spines in the battle of life, for when attacked they either roll themselves up into a ball like a hedgehog, or burrow down into the sand so fast that they seem to sink into it, leaving only the points of their prickles sticking out to pierce the feet of their enemy. Now these creatures have a little fold of skin under their body, which forms two little pouches over the milk-giving holes, and the little echidna when very tiny is put into this pouch, and keeps its head there while its body grows larger and sticks out beyond. In this way the Echidna can carry her child about with her, and she only turns it out to shift for itself when its prickles are hard and sharp.

You see, then, that though we began with the simplest known milk-giving animal, we are, in the Echidna, already fairly on our way to the curious pouched creatures of Australia, the "Marsupials," which, instead of a small fold, have indeed a large pouch of skin, into which they put their little ones when they are less than two inches long, and so imperfect that their legs are mere knobs, and they can do nothing more than hang on to the nipple with their round sucking mouths as if they had grown to it.

There the little ones hang day and night, and their mother from time t time pumps milk into their mouth, while they breathe by a peculiar arrangement of the windpipe, which reaches up to the back of their nose. Then, as they grow, the pouch stretches, and by-and-by they begin first to peep out, and then to jump out and in, and feed on grass as well as their mother's milk. For a long time they take refuge in the pouch whenever there is any danger or they are tired, and Professor Owen has suggested that this curious pouch arrangement may be of great use in a country where water is often so far to seek that the little ones could not travel to it unless the mother could carry them.

Now this race of pouched animals we find spreading all over a land where they had none of the higher four-footed animals to dispute the ground with them, for there are no ordinary land mammalia in except bats, which could fly thither; mice and rats, which could be carried on floating wood, and a fierce native dog, the Dingo, which was probably brought by the earliest native settlers long after the marsupials had spread and multiplied. And what is more, though we find the bones of marsupials of all sizes buried in the rocks of Australia, some of them as large as elephants, showing that these creatures too had their time of greatness, we do not find those of ordinary mammalia. It would seem, then, that for long ages the pouched animals had the field to themselves, and they made good use of it, filling all the different situations which in other parts of the world are filled by ordinary four-footed creatures.

On the plains, mountains, and red stony ridges are the long-legged Kangaroos every child knows so well in the Zoological Gardens. There they browse upon the grass and leaves as our cattle do in Europe, and some of them, such as the great gray Kangaroo, grow to be as much as five feet high, and can make a good fight even against the fierce dingo dog, hugging him in their arms and ripping him up with the strong nail of the long middle toe of their hind foot, which answers in them to the hoofs of our cattle and deer. And yet they are peaceable enough unless attacked, as they lurk among the tall ferns and grass, and will far rather leap away than turn and attack an enemy. Others are much smaller, such as the Kangaroo Rats, which feed on roots and grasses, one of them, the Tufted-Tailed Kangaroo-Rat, biting off tufts of grass and carrying them in his tail to make a soft nest to sleep in; while the Tree Kangaroos of New Guinea live in the trees, feeding on the leaves and jumping from bough to bough.

All these, from their long hind legs and jumping movements, we should recognise at once; but the plump furry Wombat (see Fig. 52) looks more like an ordinary four-footed animal, as it wanders by night burrowing and gnawing the roots of plants. So too do the tree-climbing animals, the Kaola or tailless bear (Fig. 51), which often carries its young one on its back, and the beautiful Phalangers or "Australian Opossums," which live in hollow trees and come out on moonlight nights to feed upon the leaves, hanging from the boughs by their long prehensile tails. Yet all these animals have a pouch for their young, and while the long-tailed furry Phalangers play the part of the fruit-eating monkeys in a land where monkeys have probably never been, another group of them, the "Flying Phalangers" (Fig. 51), with a membrane stretching between their front and hind legs, represent the flying squirrels, and live at the very top of the gum trees, feeding on leaves and flowers, and taking flying leaps with their limbs outspread.

These are all vegetable-feeders; and they leave plenty of room for the little insect-feeders, the Myrmecobius, with its long bushy tail, and the Bandicoots or rabbit-rats, which feed partly on bulbs and roots, and more often on insects, grubs, and even small mice and vermin.

But where are the animal-eaters? Surely here, as in other parts of the world, some of the group have taken to feeding on their neighbours? There are very few carnivorous animals in Australia, and these are small, though fierce, and feed chiefly on rats and mice; yet the bones of huge marsupials, with long pointed teeth, found in the rocks, tell us that dangerous animals were once there before they were driven out, probably by the Dingo and savage man. And when we get to Tasmania, where no Dingos are found, there the flesh-eating marsupials still live, as fierce as any wolves and wild cats of Europe, and still they are pouch-bearers. Slim and elegant as the fierce and furry Tiger-wolf (Fig. 52) looks as he courses over the Tasmanian plains in search of prey, yet the mother carries her young in a pouch like the gentler wombat or the powerful kangaroo; and so does the mother of the Native Devil or Tiger-cat (Fig. 52), which is so fierce that even the natives are afraid of it when it turns at bay, and it will attack and devour large sheep, though it is only the size of a terrier dog.

We see, then, that the marsupials in a world of their own, cut off by the sea from the struggling world beyond, play all parts in life; and squirrels, monkeys, insect-eaters, gnawing animals, hoofed animals, and beasts of prey, all have their parallel among the pouch-bearers. But just because they are so isolated it becomes a curious question why, when we travel right across the wide Atlantic or Pacific to America, we find another set of pouched animals slightly different but belonging to the same group. How comes it that the clever little opossums of Guiana, Brazil, and Virginia (see Fig. 53, p. 200), which grasp the trees with the free nailless great toe of their hind feet and hang by their long tails, should be marsupials, carrying their little ones in pouches, when all their relations are thousands of miles away over the sea?

Stop a moment, and let us go back to those times when the marsupials were living with the great flying reptiles in Europe and North America. These forms (see p. 183) were like the little myrmecobius now living in Australia, and at some period, we do not know exactly when, their descendants must have found their way to that part of the world, where they have since branched out into so many curious forms, gnawing, leaping, running, and flying, and filling the place of ordinary quadrupeds. But they must also have lived on in the Northern hemisphere and branched out into other forms; for much later, when tigers and other ferocious beasts had begun to prowl about in the forests of Europe and America, opossums were leaping in the trees, as we know by finding their bones in Suffolk, under Paris, and in North America. And so we see that when these opossums found their way down south to Brazil and Guiana, the simile that we used a little while ago (p. 131) probably became literally true, and the Australian and South American pouched animals are related to each other, not because they come one from the other, but because they both come from the same very ancient stock which once lived in Europe.

This would explain how these active, furry, little beings of all sizes, from that of a good-sized cat to a rat, come to be sporting among the leaves of the grand forests of Brazil or on the edges of the Virginian swamps, sleeping during the day in the hollow trees, and prowling by night over the plantations, and among the rice-fields feeding on fruit and seeds, worms and insects, and even on young birds and rats. On the ground they walk heavily, with flat feet, but in the trees they swing from bough to bough (see Fig. 53), the little ones curling their tails round that of their mother and clinging to her back as she goes. Some of these opossums have even lost the pouch, and put their little ones at once on to the thick fur of their back as soon as they come out of their snug nests in the tree-hollows. They seem to have a happy time of it, these merry tree-climbers, and know well how to swing out of danger, or to feign death if they cannot escape, so that " 'cute as a 'possum" is a common American proverb. One kind, living in the swamps of Guiana, feeds almost entirely on crabs, while another, called the Yapock, has webbed feet and dives under water, feeding on fish and other water-animals.

But here another question presents itself. How is it that these curious pouched animals have lived on in America as well as in Australia when they have been killed off in Europe and Asia? The answer to this is not far to seek if we remember that geology teaches us that there have been many changes of land and sea in past times, for the neck of land which joins South America to North America is very low and narrow, and a change of level of scarcely more than 2000 feet would break it up into islands; and as we know that such changes have taken place in past geological times, there is no doubt that once this neck was partially under the sea, and South America, like Australia, was a huge continental island, where the lower animals might struggle on and become settled, before the higher ones poured in to interfere with them.

Indeed, if the opossums did not teach us this history, we might learn it from another singularly old-fashioned race of animals; for in the same Brazilian forests in which our little opossums are sporting, the dreamy Sloth, with his long arms, short legs with the knees bent outwards, and long thick hair drooping over his eyes, is hanging back downwards from the boughs; while the strange Ant-bear is tearing open the ant-hills with his strong bent claws in the damp earth below, and licking up the insects with his long sticky tongue; and the Armadillo, whose back is covered with bony shields like the crocodile, issues out of his burrow at night to dig for worms or roots or buried animals. We may look all the world over and we shall not find another group so strange and old-fashioned as this one, nor even any creatures of their kind, except the ant-eaters of the Cape and the scaly Manises of Africa and India, which also live, as you will notice, upon continents which jut out into the water, and not on the great northern mass of land.

In many ways these curious animals (Edentata ) of South America and Africa are more singular, though not of so ancient a race, as the "pouch-bearers." Many of them, the American ant-bears and the African Pangolins, are quite toothless, and those which like the sloth have teeth, have very imperfect ones more like the teeth of reptiles than those of marsupials; again, their feet have the toes much joined together, and the sloths have only three toes on the hind feet and sometimes two only on the front, and the joints of their neck are irregular in number. Thus we see in them that variability of structure which always points to a low order of animals; and, moreover, the armadilloes are the only milk-giving animals which are covered with bony plates like reptiles.

What, then, is the history of these old-fashioned animals? Much the same as that of the marsupials, so far as we can read it; for at the same time that opossums were living in Europe, strange animals, with imperfect rootless teeth, and toes with immense claws, bent inwards like the claws of the ant-eaters, were wandering over France and Greece, where we now find their bones. Then a little later we find, on the shores of the Pacific in North America, other huge imperfect-toothed creatures, which lived, died, and were buried in the mud; and lastly, in South America, still later, we find whole skeletons of gigantic sloth-like animals the size of elephants, which had not yet such long arms as the Sloth of to-day, but walked on four feet upon the ground and browsed upon the trees, while huge armadillo-like creatures, with solid bony shields covering their backs, wandered in the vast forests and lived on animal food. Making use of these facts, then, cannot we picture to ourselves how these large unwieldy creatures, with their stiff bent claws and their weakly teeth, which if once broken or lost could not be replaced by a second set, were no match for the large tigers, bears, and other beasts of prey which were roaming over Europe and Asia; while those, on the contrary, which found their way from North to South America, and were cut off from the crowded world, just as the marsupials were, might live on and fill the land with large creepers and burrowers. In the old world the same would probably happen in Africa, where the sea certainly flowed at one time over the low-lying desert of Sahara; and so the Cape Ant-eater and the Pangolin, both so different from their American relations, would keep their place in the world.

This would explain how they gained a firm footing; but the next question is how they kept it, when jaguars and pumas began to roam over America, and lions and panthers over Africa? Now, if we inquire into the history of the Aard-Vark or great Cape ant-eater, which is in many ways much more like the American armadilloes,—for he has like them teeth in the back of his mouth, and walks flat-footed, though he has a thick skin and bristles instead of armour,—we find that he is a very timid animal, and lives almost entirely underground, only venturing out at night to scratch open the ant-hills with his strong claws, so that he may thrust his long sticky tongue into the ant-galleries to draw it back covered with food. Even then he never ventures far from his hole, so we can easily conjecture that it is by concealment that he has escaped destruction.

Still more would the Pangolins flourish, for though they are toothless and walk very clumsily, because their front feet are bent under so that they tread on the upper part, yet they have two means of First, like the ant-eater, they live chiefly underground and come out at night; and secondly, their back is covered with sharp-edged scales, which grow from the skin as hairs do, and can be raised into a complete cheval-de-frise  as they roll themselves up, or tuck their tail and head between their legs when they are attacked. Thus protected, the scaly ant-eaters not only flourish in Africa, but have even kept their ground in India, China, and Ceylon.

In America, on the other hand, we find that the armadilloes have gone strangely back to the bony armour of the reptiles or the ancient Labyrinthodonts, and have shields on their backs and heads formed of skin-plates exactly like those of the crocodile, so that the only delicate part of their body is the under side, which is kept close to the ground. When we see how well they are protected, and also remember that they are extremely quick burrowers and can get out of the way of dangerous enemies, while they feed on vegetables, insects, and dead creatures, we see why the plains and forests of South America should abound in armadilloes of all sizes, from the Great Armadillo, as large as a moderate-sized pig, to the little Pichiciago, not larger than a rat.

It would be more difficult to understand how the great hairy Ant-bear (p. 200), with his twisted feet, united toes, and toothless tube-like snout, has managed to live on in the dense forests of South America, if we did not know that he is immensely strong, and his sharp claws and the deadly hug of his-muscular arms are avoided even by large animals, while the small American Ant-eaters live chiefly in the trees, feeding on bees, termites, and honey. A strange fellow is the great ant-bear as he wanders at night slowly and heavily along the river-banks, his long bushy tail sweeping behind him and his head bent low; or, if it be a mother, she may be carrying her little one clinging to her back, or pause to hold it in her long arms as it sucks. Be this as it may, by-and-by the ant-bear reaches a group of nests of termites (wrongly called white ants), looming six feet high in the dark night; at once the sharp claws are at work tearing the hill to pieces, though they arc so strongly built that men have to open them with a crowbar, and as the alarmed termites rush out, the long sticky tongue wanders among them and they are drawn into the ant-bear's mouth by thousands. Yet the ant-bear has his enemies, for it may be that in his night-walk he may come across the fierce jaguar in search of prey.

Now, D'Azara, the great traveller, doubted the stories of the natives when they said that the ant-bear could kill the jaguar, but Mr. Cumberland, who has lived much in South America and has himself killed the ant-bear, assures me that the animal is quite a match for such a wild beast. The muscles of his shoulder and arms arc tremendous, the claws so hard and strong and sharp that when once stuck in they never lose their hold, and the ant-bear when attacked stands up and gives a death-hug so dreadful that the natives never dare to come to close quarters with him. Moreover, he is very difficult to kill. Mr. Cumberland, by the help of his dog and man, caught and disabled one of these creatures so as to tie his legs together and keep him stunned, but his skull was so hard that repeated blows with heavy quartz rock on his nose, the most vulnerable point, only succeeded in stunning him, and his skin was so tough that an ordinary small dagger-knife made no impression whatever. With all their efforts they could not put the poor animal to death till the following morning, when they could get a strong and sharp knife to butcher him. Such a creature as this need scarcely fear a jaguar or any beast of moderate size.

Such, however, is not the case with the dull-looking hairy forms which move among the tall cecropia trees above the ant-bear's head; for the sloths, though busy enough in the trees, would fare but badly if they were condemned to live upon the ground. The sloth is surely one of the most curious examples of how an animal may live and flourish by taking to a strange way of life. We have seen (p. 202) how his ancestors, the Megatheriums, walked upon the ground, while he himself was formerly pitied by all travellers because his arms are so long in comparison with his legs that if he wants to walk he has to drag himself along upon his elbows, and while the ankles of his hind feet are so twisted that he can only rest on the side of the foot. But then they forgot that he seldom or never descends to the ground, for the buds and leaves of the trees are his food, and they are so juicy that he does not need to come down to drink, and when he is in his natural place in the trees he is no longer helpless.

There, safe from prowling animals on the ground below, he hangs like a hammock from the bough. The long fingers of his hand (in some sloths two, in others three, in number) and the three toes of his twisted hind feet, all armed with long claws, seize the branch like grappling irons; while his long flexible neck, which in one kind of sloth has more joints than in other mammalia, enables him to look over his shoulder and take a wide survey around. In the daytime he sleeps with his back in the fork of a branch and his head bent forward on his chest, but as the sun goes down he rouses to life and feeds by stretching out those long arms to tear the leaves and twigs, which he stuffs into his mouth and chews with his few back teeth. He has no need to hurry or disturb himself, for his long thick hair protects him from insects; and from the very fact of his being fitted for a tree-life he is safe from other animals except snakes, and even they do not find him out easily, so like is his dull matted hair to the colour of the bark and moss. Even the young ones run very few risks, for they are not born till they are perfect, and then the baby sloth clings to its mother's hair, and goes with her wherever she travels, sucking till it is old enough to hang on to a bough and feed itself. So they live a completely tree-life, and sleepy as they seem, yet they can move quickly enough when they wish; and they often take advantage of a time when the wind is blowing so that the branches from tree to tree sway against each other, and by seizing the boughs as they touch, pass along and find new feeding-grounds.

We see, then, that while the duck-billed water-mole and the echidna have found a comparatively peaceful home in Australia, where the pouched animals have reigned as monarchs, and still hold their own in spite of the animals brought in by man; and while the opossums, by taking to a tree-life, revel in the forests of America: so the imperfect-toothed animals, an old and antiquated race of Life's children, still remain in a few scattered forms by reason of their power to adapt themselves to peculiar conditions of life. What they may have been in olden times we can scarcely guess; but one thing is certain, namely, that before such strangely different forms as the sloth, the ant-eater, the manis, and the armadillo could each have settled down and taken on their special protective armour and habits, many others must have tried, flourished awhile, and died out. When we look at the bones of the gigantic Ground-sloths or Megatheriums of olden times, which walked on four feet and are supposed to have lived by tearing the trees up by the roots and feeding on the branches, or when we examine the huge shield of the monster Glyptodon, and find that it had no movable bands between the plates such as enable the armadillo to burrow with ease, or in some kinds to roll up in a ball, we see that it is not always size and strength that win in the battle of life; but that the sloth of to-day has probably lived on because, in taking refuge in the trees, it has secured great advantages by those peculiarly long arms and twisted feet for which men used to pity it; while the anteaters and armadilloes in their underground homes, and the pangolins rolled up into prickly balls, show that passive resistance and retiring habits, especially if fortified by a thick skin, are sometimes quite as useful in the struggle for existence as fierce passions and aggressive weapons.