And when we go into the quiet country, leaving man and his works behind, how actively we find life employed! Covering every inch of the ground with tiny plants, rearing tall trees in the forest, filling the stagnant pools full of eager restless beings; anywhere, everywhere, life is at work. Look at the little water-beetles skimming on the surface of the shady wayside pool, watch the snails feeding on the muddy bank, notice the newts putting their heads above water to take breath, and then remember that, besides these and innumerable other animals visible to the naked eye, the fairy-shrimp and the water-flea, and other minute creatures, are probably darting across the pond, or floating lazily near its surface; while the very scum which is blown in ridges towards one corner of the pool is made up of microscopic animals and plants.

Then, as we pass over plain, and valley, and mountain, we find things creeping innumerable, both small and great; some hidden in the moss or the thick grass, rolled up in the leaves, boring into the stems and trunks of trees, eating their way underground or into even the strongest rock; while others, such as the lion, the tiger, and the elephant, roaming over Africa and India, rule a world of their own where man counts for very little. Even in our own thickly peopled country rabbits multiply by thousands in their burrows, and come to frolic in the dusk of evening when all is still. The field-mice, land and water rats, squirrels, weasels, and badgers, have their houses above and below ground, while countless insects swarm everywhere, testifying to the abundance of life. Not content, moreover, with filling the water and covering the land, this same silent power peoples the atmosphere, where bats, butterflies, bees, and winged insects of all forms, shapes, and colours, fight their way through the ocean of air; while birds, large and small, sail among its invisible waves.

And when by and by we reach the sea, we find there masses of tangled seaweed, the plants of the salt water, while all along the shores myriads of living creatures are left by the receding tide. In the rocky pools we find active life busily at work. Thousands of acorn-shells, many of them scarcely larger than the head of a good-sized pin, cover the rocks and wave their delicate fringes in search of food. Small crabs scramble along, or swim across the pools, sand-skippers dart through the water, feeding on the delicate green seaweed, which in its turn is covered with minute shells not visible to the naked eye, and yet each containing a living being.

Wherever we go, living creatures are to be found, and even if we sail away over the deep silent ocean and seek what is in its depths, there again we find abundance of life, from the large fish and other which glide noiselessly along, lords of the ocean, down to the jelly-masses floating on the surface, and the banks of rocky coral built by jelly-animals in the midst of the dashing waves. There is no spot on the surface of the earth, in the depths of the ocean, or in the lower currents of the air, which is not filled with life whenever and wherever there is room. The one great law which all living beings obey is to "increase, multiply, and replenish the earth;" and there has been no halting in this work from the day when first into our planet from the bosom of the great Creator was breathed the breath of life,—the invisible mother ever taking shape in her children.

No matter whether there is room for more living forms or not, still they are launched into the world. The little seed, which will be stifled by other plants before it can put forth its leaves, nevertheless thrusts its tiny root into the ground and tries to send a feeble shoot upwards. Thousands and millions of insects are born into the world every moment, which can never live because there is not food enough for all. If there were only one single plant in the whole world to-day, and it produced fifty seeds in a year and could multiply unchecked, its descendants would cover the whole globe in nine years. But, since other plants prevent it from spreading, thousands and thousands of its seeds and young plants must be formed only to perish. In the same way one pair of birds having four young ones each year, would, if all their children and descendants lived and multiplied, produce two thousand million  in fifteen years, but since there is not room for them, all but a very few must die.

What can be the use of this terrible overcrowding in our little world? Why does this irresistible living breath go on so madly, urging one little being after another into existence? Would it not be better if only enough were born to have plenty of room and to live comfortably?

Wait a while before you decide, and think what every creature needs to keep it alive. Plants, it is true, can live on water and air, but animals cannot; and if there were not myriads of plants to spare in the world, there would not be enough for food. Then consider again how many animals live upon each other; if worms, snails, and insects, were not over-abundant, how would the birds live? Upon what would lions, and tigers, and wolves feed if other animals were not plentiful; while, on the other hand, if a great number of larger animals did not die and decay, what would the flesh-feeding snails, and maggots, and other insects find to eat? And so we see that for this reason alone there is some excuse for the over-abundance of creatures which life thrusts into the world.

But there is something deeper than this to consider. If in a large school every boy had a prize at the end of the half-year, whether he had worked or not, do you think all the boys would work as hard as they do or learn as well? If every man had all he required, and could live comfortably, and bring up his children to enjoy life without working for it, do you think people would take such trouble to learn trades and professions, and to improve so as to be more able than others? Would they work hard day and night to make new inventions, or discover new lands, and found fresh colonies, or be in any way so useful, or learn so much as they do now?

No, it is the struggle for life and the necessity for work which makes people invent, and plan, and improve themselves and things around them. And so it is also with plants and animals. Life has to educate all her children, and she does it by giving the prize of success, health, strength, and enjoyment to those who can best fight the battle of existence, and do their work best in the world.

Every plant and every animal which is born upon the earth has to get its own food and earn its own livelihood, and to protect itself from the attacks of others. Would the spider toil so industriously to spin her web if food came to her without any exertion on her part? Would the caddis worm have learnt to build a tube of sand and shells to protect its soft body, or the oyster to take lime from the sea-water to form a strong shell for its home, if they had no enemies to struggle against, and needed no protection? Would the bird have learnt to build her nest or the beaver his house if there was no need for their industry?

But as it is, since the whole world is teeming with life, and countless numbers of seeds and eggs and young beginnings of creatures are only waiting for the chance to fill any vacant nook or corner, every living thing must learn to do its best and to find the place where it can succeed best and is least likely to be destroyed by others. And so it comes to pass that the whole planet is used to the best advantage, and life teaches her children to get all the good out of it that they can.

If the ocean and the rivers be full, then some must learn to live on the land, and so we have for example sea-snails and land-snails; and whereas the one kind can only breathe by gills in the water, the other breathes air by means of air-chambers, while between these are some marsh-snails of the tropics, which combine both, and can breathe in both water and air. We have large whales sailing as monarchs of the ocean, and walruses and seals fishing in its depths for their food, while all other animals of the mammalian class live on the land.

Then, again, while many creatures love the bright light, others take advantage of the dark corners where room is left for them to live. You can scarcely lift a stone by the seaside without finding some living thing under it, nor turn up a spadeful of earth without disturbing some little creature which is content to find its home and its food in the dark ground. Nay, many animals for whom there is no chance of life on the earth, in the water, or in the air, find a refuge in the bodies of other animals and feed on them.

But in order that all these creatures may live, each in its different way, they must have their own particular tools to work with, and weapons with which to defend themselves. Now all the tools and weapons of an animal grow upon its body. It works and fights with its teeth, its claws, its tail, its sting, or its feelers; or it constructs cunning traps by means of material which it gives out from its own body, like the spider. It hides from its enemies by having a shape or colour like the rocks or the leaves, the grass or the water, which surround it. It provides for its young ones either by getting food for them, or by putting them, even before they come out of the egg, into places where their food is ready for them as soon as they are born.

So that the whole life of an animal depends upon the way in which its body is made; and it will lead quite a different existence according to the kind of tools with which life provides it, and the instincts which a long education has been teaching to its ancestors for ages past. It will have its own peculiar struggles, and difficulties, and successes, and enjoyments, according to the kind of bodily powers which it possesses, and the study of these helps us to understand its manner of existence.

And now, since we live in the world with all these numerous companions, which lead, many of them, such curious lives, trying like ourselves to make the best of their short time here, is it not worth while to learn something about them? May we not gain some useful hints by watching their contrivances, sympathizing with their difficulties, and studying their history? And above all, shall we not have something more to love and to care for when we have made acquaintance with some of Life's other children besides ourselves?

The one great difficulty, however, in our way, is how to make acquaintance with such a vast multitude. Most of us have read anecdotes about one animal or another, but this does not give us any clue to the history of the whole animal world; and without some such clue, the few observations we can make for ourselves are very unsatisfactory. On the other hand, most people will confess that books on zoology, where accounts are given of the structure of different classes of animals, though very necessary, are rather dull, and do not seem to help us much towards understanding and loving these our fellow-creatures.

What we most want to learn is something of the lives  of the different classes of animals, so that when we see some creature running away from us in the woods, or swimming in the pond, or darting through the air, or creeping on the ground, we may have an idea what its object is in life—how it is enjoying itself, what food it is seeking, or from what enemy it is flying.

And fortunately for us there is an order and arrangement in this immense multitude, and in the same way as we can read and understand the history of the different nations which form the great human family spread over the earth, and can enter into their feelings and their struggles though we cannot know all the people themselves; so with a little trouble we may learn to picture to ourselves the general life and habits of the different branches of the still greater family of Life, so as to be ready, by and by, to make personal acquaintance with any particular creature if he comes in our way.

This is what we propose to do in the following chapters, and we must first consider what are the chief divisions of our subject, and over what ground we have to travel. It is clear that both plants and animals are the children of Life, and indeed among the simplest living forms it is often difficult to say whether they are plants or animals.

But it is impossible for us to follow out the history of both these great branches or Kingdoms, as naturalists call them, so we must reluctantly turn our backs for the present upon the wonderful secrets of plant life, and give ourselves up in this work to the study of animals.

First  we meet with those simple forms which manage so cleverly to live without any separate parts with which to do their work. Marvellous little beings these, which live, and move, and multiply in a way quite incomprehensible as yet to us. Next we pass on to the slightly higher forms of the second  division of life, in which the members have some simple weapons of attack and defence. Here we come first upon the wonderful living sponge, building its numerous canals, which are swept by special scavengers; these form a sort of separate group, hovering between the first  and second  division, and from them we go on to the travelling jelly-fish, with their rudiments of eyes and ears, and their benumbing sting, and then to the sea-anemones with their lasso-cells, and to the wondrous coral-builders. Already we are beginning to find that the need of defence causes life to arm her children.

The third  division is a small, yet most curious one, containing the star-fish with their countless sucker-feet, the sea-urchins with their delicate sharp spines and curious teeth, and the sea-cucumbers with their power of throwing away the inside of their body and growing it afresh. This division goes off in one direction, while the next, or fourth, though with creatures almost as simple as the coral-builders, takes quite a different line, having for its members mussels and snails, cuttle-fish and oyster, and dividing into two curious groups: the one of the shell-fish with heads, and the other of those without any.

The fifth  division, starting also in its own line by the side of the third and fourth, includes the creeping worms provided with quite a different set of weapons, and working in their own peculiar fashion, some living in the water, some on the earth, and some in the flesh of other beings, feeding upon their living tissues. An ugly division this, and yet when we come to study it we shall find it full of curious forms showing strange habits and ways.

The sixth  division is a vast army in itself, with four chief groups all agreeing in their members having jointed feet, and subdivided into smaller groups almost without number. The first group, including the crabs and their companions, live in the water, and their weapons are so varied and numerous that it will be difficult for us even to gain some general idea of them. The other three groups, the centipedes, spiders, and six-legged insects, breathe only in the air. This sixth or jointed-legged division contains more than four-fifths of the whole of the living beings on our globe, and it forms a world of its own, full of interest and wonders. In it we have all the strange facts of metamorphosis, the wondrous contrivances and constructions of insect-life, and at the head of it those clever societies of wasps, bees, and ants, with laws sometimes even nearer to perfection than those of man himself.

Lastly we come to the seventh  and vast division of back-boned animals which will claim a separate volume to itself. This division has struggled side by side with the other six till it has won a position in many respects above them all. Nearly all the animals which we know best belong to it,—the fishes, toads, and newts (amphibia), the reptiles, the birds and the mammalia, including all our four-footed animals, as well as the whales, seals, monkeys, and man himself.

Under these seven divisions then are grouped the whole of the living animals as they are spread over the earth to fight the battle of life. Though in many places the battle is fierce, and each one must fight remorselessly for himself and his little ones, yet the struggle consists chiefly in all the members of the various brigades doing their work in life to the best of their power, so that all, while they live, may lead a healthy, active existence.

The little bird is fighting his battle when he builds his nest and seeks food for his mate and his little ones; and though in doing this he must kill the worm, and may perhaps by and by fall a victim himself to the hungry hawk, yet the worm heeds nothing of its danger till its life comes to an end, and the bird trills his merry song after his breakfast and enjoys his life without thinking of perils to come.

So life sends her children forth, and it remains for us to learn something of their history. If we could but know it all, and the thousands of different ways in which the beings around us struggle and live, we should be overwhelmed with wonder. Even as it is we may perhaps hope to gain such a glimpse of the labours of this great multitude as may lead us to wish to fight our own battle bravely, and to work, and strive, and bear patiently, if only that we may be worthy to stand at the head of the vast family of Life's children.