The puzzle of life and how it has been put together

We must now go back and collect the smaller pieces of “the puzzle” which make up the animal part. The great periods of vegetation ended in our country with the coal forests, and there has been no such wonderful growth of plants since the time when the New Red Sandstone, lying above the coal, was formed; though no doubt trees and plants have since flourished, as they do now on the Earth, but not in such quantities as during the coal period.

We remember that the eozöon, “the life-dawn animal,” is the oldest animal we know of, and that it lived so long ago as when the Laurentian rocks were laid down at the bottom of the seas of that time; then in later rocks we find the burrows of sea worms in the stone, and later still simple shells with two valves like the common mussel, and other animals of a simple kind, like the corals, sponges, and star-fishes which exist now. There must have been millions of these creatures in the older limestone seas, for the rocks are almost entirely composed of their fossil shells and bodies. By-and-by a rather superior animal inhabited the seas of Wales, called a trilobite, of which you will see a picture on the opposite page. This curious animal was of the same family as the shrimps and prawns, but much larger, and he must have been a giant among the others. None of these animals had any bones, you must understand; but they had a hard shelly covering to support their soft bodies inside, and no doubt the trilobites were able to swim about very fast.[7]

What I want you to take notice of now is the progress that has been going on from the almost motionless eozöon to the shell-fish and star-fish, which could crawl along the bottom of the sea and over the rocks, to this active, quick-moving trilobite, with his great paddles. Then the next step is a very great one, when we come to animals with bones. The first of these are fishes. All the other bones are joined to the backbone, therefore all animals with bones are called vertebrata, which is a Latin word meaning having a backbone with joints. Now animals with bones are plainly superior to those with only shells, and when we find fishes among the rocks of Wales and Devonshire we know that we are beginning to pick up some important pieces of the “puzzle of life.” These fishes were most of them related to the sturgeon, and their bones and teeth are found in great quantities in the Old Red Sandstone rocks, just below the coal.[8]

It is not until we get above the coal into the oolite or egg-stone rocks that still larger and altogether superior animals, both of sea and land, began to increase, and this is called

THE AGE OF REPTILES.

This has been called the reptile age because there were such numbers of animals like crocodiles, lizards, and tortoises (which are all reptiles), and some of them were of immense size. For instance, there was a huge creature something like a frog, but as large as a Shetland pony, called the Labyrinthodon, with a great many curious teeth, and this animal has left footprints in the New Red Sandstone which have been dried and buried, we can’t tell how long, and there are the cracks made by the sun drying the place he walked over when that was soft earth. There is a drawing of some of these footsteps in the picture on the next page, and there are also the footprints of a large bird, and you can see where he walked over the soft earth and made a long line of footmarks; and if you look at the footprints of birds on the snow or mud now you will notice marks just like these. Then there is another picture of a single footprint of a large bird, and all those round dots are where rain-drops fell and left their marks in the soft earth.

I dare say you will wonder how it is that these footprints have not disappeared. Well, when the animals and birds that made them had gone the marks became filled with dry sand, no doubt blown in by the wind, and then the mud dried hard, and at last it became covered with other earths and sank slowly down, just as the coal forests had done before, and remained there until we dug it up with these tracks of the birds and animals that lived then. Some of these birds must have been larger than any living now, because their footmarks are so long. None of their bones have been found yet, I believe, but plenty of the teeth and some bones of the labyrinthodon have. The real footmarks, of course, are very large, though they are small in the picture.[9]

In the great beds of Lias there are many other strange animals, and among them are two great fish-lizards called the Ichthyosaurus and Plesiosaurus. Both of these lived in the water and perhaps came on land sometimes, and it is certain that they must have been very ferocious creatures, from their great size and sharp teeth. The plesiosaurus would be able to raise his long neck above the water and snap at some of those curious birds rather like bats which lived at the time, and of which I shall have something to say presently. Some of these fish-lizards were as large as whales, and their bodies have been so beautifully preserved in the limestone rocks that we can actually sometimes find in their stomachs the food they lived on.

Now we have got to a higher order of creation still, these fish-lizards, and they remind one of the next step in progress—birds. You know that all birds lay eggs, so do almost all reptiles, such as crocodiles, lizards, and most snakes, so that they are alike in this. Then the plesiosaurus with his long neck reminds us of such birds as the heron and the swan, but he is altogether more like a reptile than either a fish or a bird. There were also huge land reptiles, which lived in the forests of the time, and must have been a terror to the smaller animals. From the bones of one of these which have been found in the oolite clays near Weymouth in Dorsetshire (the Cetiosaurus), we see that it must have been nearly as large as an elephant, and there are others called the Megalosaurus, Dinosaurus, &c. All these names end with saurus, a name taken from the Greek word meaning lizard; and you will see now why the oolite, or “Jurassic”[10] age, as it is sometimes called, is well named the “reptile age,” for these creatures swarmed on the land and in the sea. Specimens of these you can see for yourselves in the cases on the walls of the third room in the North Gallery of the British Museum, where all the fossils are collected.

But still more extraordinary animals than any of these lived at the time, and we can scarcely tell whether they were birds or reptiles, as they were something like both, but I suppose we must call them flying reptiles, and they are the nearest approach to birds that had yet existed. These creatures are called Pterodactyles, from two Greek words which mean “wing-fingered.” Suppose the little fingers of both your hands were a yard longer than the others, and suppose a thick leathery skin was stretched from the tips of your long little fingers to each of your feet, you would have wings something like a pterodactyl and also something like the wings of a bat. But the pterodactyl had a long neck and a long beak-like mouth, full of long sharp pointed teeth. It could not walk much I think, but it could hang itself up by its hind limbs to a tree or rock, head downwards like a bat, and must have been able to fly very strongly, with its huge leathery wings, but it had no feathers. There were swarms of these curious half lizard half bird-like animals on the land, and they were of all sizes, some no bigger than a crow, and some as large as the albatross, measuring twelve feet across their outstretched wings. Their skeletons are some of the commonest fossils in the oolite rocks, all through the great reptile age.[11]

Now you see we have come to a reptile that can fly, but, excepting for its wings and some of its bones, more like a crocodile than a bird. A little further on we find another curious animal in the oolite rocks, which is much more like a true bird than the pterodactyl, because it had feathered wings. It is called the Archæopteryx, which means “ancient wing,” and I have given a picture of it on the same page as the pterodactyl, so that you may compare them together. The blade-bone and “merry-thought” of this creature were exactly like those of a bird, and so were the feet and legs, which would enable it to walk easily, or perch on the branch of a tree, but the tail was long and many-jointed like that of a lizard, with a fan of feathers growing on each side of it, and short feathered wings. Then it most likely had teeth like a lizard, and there were short claws at the bend of the wings. This bird-reptile was about the size of a crow, and was the first we know of with feathers, and the limestone rock has preserved it most beautifully through all the long ages which have passed since it flitted over the land of the oolite period.[12] Later still than these, there lived in America, about the time the chalk was formed in England, two strange birds called Hesperornis and Ichthyornis, both of which had teeth in the jaws. The former was an immense fellow like the penguin, with short wings, and the latter was about the size of a pigeon with large feathered wings.

They are finding more of these curious creatures every now and then in America. Some are without teeth, and have a horny bill like that of a real bird, and in other ways more nearly resemble living birds; still they have not lost the appearance of reptiles in their principal bones.

I have been particular in describing some of these fish-lizards and bird-reptiles; because they, or their near relations, were the principal inhabitants of land and sea from the end of the coal period to the end of the chalk, though there were of course swarms of fishes and shell-fish; but I ought to tell you that even so early as this there was at least one animal known which suckled its young ones, and this was a small insect-eating creature not larger than a rat, of the same family (called Marsupial) as the kangaroo of Australia, which carries its young ones in a pocket or pouch in its skin.

All this time we have been hunting for parts of “the puzzle” in those ancient oolite rocks between the coal and the chalk, and those we have found are very important. We have seen the slow progress from simple sea shells to simple fishes, and then onwards to fish-lizards and bird-reptiles with one little marsupial animal, of a far higher kind, in between, as if to tell us beforehand what more complete and perfect animals we might expect by-and-by. After the fishes we have found fish-lizards, then bird-reptiles with wings, but no feathers, and later still a bird-reptile with wing and tail feathers. How different the life of the Earth was at the end of the “reptile age” of the oolite rocks, to the far back Laurentian time when one little creature, our old friend eozöon, alone held possession of the seas!

THE CRETACEOUS PERIOD.

Now let us look into the rocks next above, and see what is to be found there. We have arrived in the Cretaceous period, or time when the chalk was formed.[13] You remember I told you you might call this “foraminifera earth” because so much of it was made up of the shells of these tiny animals, thousands of which could be put into a thimble. Whenever you make a mark with a piece of drawing chalk you rub off a number of them, and you will see what pretty little creatures they were if you look at the drawings of some of them on the next page as they are seen under the microscope, magnified thousands of times their natural size; but there are others of different shapes. On the same page too there is a handsome shell, called an ammonite, and of its real size, common in chalk rocks. The seas of the time must have been very deep as I have explained before, and the chalk contains numbers of bones of fishes everywhere, and many of the remains of the reptile-like creatures of the time before. Corals, sea-urchins, crabs, &c., abounded, and as you can scarcely ever see chalk without immense flint stones in it, you may suppose what millions of sponges lived on the rocks, for these flints are partly made up of their fossil bodies.[14] Another Cretaceous period is beginning now at the bottom of the Atlantic and Pacific Oceans, where it is deep enough to cover the Alps, for these little foraminifera are living on the surface in countless millions, and day by day their fossil shells are settling down to the bottom and forming a soft grey mud, full of the carbonate of lime like chalk. The climate of the Cretaceous age was mild and pleasant, as we know from the kind of animals in the seas. Slowly the water began to get shallower and shallower by the upheaval of the bed, and at last the bottom of this mighty chalk ocean came up to the light and sun, to be covered in some places with the drift and worn particles of older rocks swept over it by rivers, and to receive new plants and new animals, and in some places to remain almost bare, as it is on the downs of Brighton.

Now we take one more step upwards into almost a new world—the world on which mighty animals lived, and which man came to share with them.

THE TERTIARY PERIOD.

The reign of the reptiles is now passed. The ichthyosaurus and pterodactyl no longer inhabited the seas and continents. Great changes had taken place in the shape of the land. A river larger than the Rhine swept majestically through England from the borders of Wales right out into the German Ocean, and its banks were covered with forests and marshes, where the new animals which had come to take possession of the earth lived and moved and had their being. The mountains of the Pyrenees were raised above the sea, and parts of Surrey and Sussex appeared too. It was most likely in the early part of the Tertiary period that the stone was formed of which almost all Paris is built. Fancy a great city built of the shells of dead animals! One can scarcely believe it: but the microscope lets us into this secret of Nature. If we take a piece of this stone and examine it in a powerful microscope we see that it is made almost entirely of tiny shells, so small that myriads of them could be packed in a nut-shell. How long must they have been working to make all the stone beds of which Paris is built? We cannot measure the time, we can only know it must have been enormous!

All kinds of animals both of sea and land increased in numbers and perfection. The ammonites were dead, but their even more beautiful relation, the nautilus, was living as it is now. The trilobite was gone, but his next relation, the lobster and crab, appeared. Fishes abounded. Whales which suckle their young ones appeared, and the numbers of vertebrata, or animals with backbones, were more numerous than they had ever been before. Just as animals with bones are more perfect than those with only skins or shells, so animals which suckle their young ones are more perfect than those which only lay eggs. Thus the whale is a more perfect animal than the shark, though both inhabit the water; and elephants and even rats and mice more perfect still; and because there were so many of these “sucklers,” or mammalia as they are called, in the Tertiary period, we know that all living creatures were becoming more perfect. It will interest you too to learn that monkeys began to appear now, and that they were common in France, while at the present time the only part of Europe where they are to be found is on the rock of Gibraltar.

But I want particularly to tell you of the giant animals—the Mammoth, Mastodon, Megatherium, Dinotherium, and others, and first let us see what the mammoth was like.

In former times, when people accidentally found the bones of these animals, they actually thought they had belonged to giant men, and we can scarcely wonder at that: but we know better. If only one small bone is shown to Professor Owen or Professor Huxley, he can tell at once whether it belonged to a man or an animal, a fish or a bird, and very often the particular animal too. Well, the bones of the mammoth were found in the north of Russia on the banks of the river Lena in 1800: but the Russians knew of them before that, and the name they gave the animal means “earth,” because they supposed it burrowed in the earth like a mole. This one is now in the Museum at St. Petersburg, and its brownish coat and long black hairs, and even the hoofs and some of the flesh, can be distinctly seen. The drawing in the frontispiece is taken from it. It was strange that any people could have supposed that this huge creature, larger than an elephant and with great curved tusks ten feet long and weighing 160 lbs., could have got underground of its own accord: but that was the only way in which they could account for finding it buried in the earth on the banks of the rivers. Look at the picture in the frontispiece; what a splendid animal he was, this old elephant; larger and stronger than any living elephants! Immense quantities of their bones are found in Siberia, and the tusks and teeth are brought in ship-loads to England, where they are sold for their ivory. Their skeletons have been found in most countries of Europe, in many parts of Asia, and in North America, and these animals must have been common at one time near London, for their bones have been dug up in the brick earth at Ilford in Essex and other places near the Thames. There is a skull with tusks set up with iron supports in the British Museum.[15]

There was besides another animal very much like this called the Mastodon; but it had tusks in the lower jaws as well as the upper, four in all, and the lower tusks dropped out when the animal grew old. The whole skeleton of one of these is also put up in the Museum, which you ought to go and see.[16] Mastodons’ bones have been discovered in England and other parts of Europe, and in North and South America and India, so that they were spread pretty well all over the world. They had very curious pointed teeth rather like a lot of fir cones piled together, not flat grinders like those of the mammoth and all living elephants, and perhaps they fed upon fruits and nuts, and boughs, as I do not think they could have managed well to chew grass and leaves with such pointed teeth. The teeth in their old dead jaws are still beautifully white and look like china. Both the mammoth and the mastodon had long trunks of course, and they must have been grand looking creatures marching about in the English forests. We should be very much startled if we were to meet one of them now in an English wood: but there is no chance of that, they have all passed away, and the only relations they have living are the elephants of Africa and Asia.

During this Tertiary period, or at least the early part of it, besides the mammoth and mastodon, the hippopotamus and rhinoceros were plentiful about the Thames. Those same Ilford marshes in Essex have been a complete storehouse of the remains of these animals. The bones of a hundred different mammoths and eighty rhinoceroses have been dug up lately from the damp, black soil, as well as many belonging to the hippopotamus, and we can have no doubt that all the swamps along the north side of the river were inhabited by large herds of these huge beasts, or so many of their skeletons could not have been collected in one place. It is very likely they were overtaken in a flood of the river and drowned, and their bodies sank down in the mud of the river bank: but anyhow, there they are to tell us that they lived and died almost within sight of the Tower of London, if it had been built then, as of course it was not.

Long long ago too, before there was a single brick where London stands, and when the few human beings who were living were obliged to hide themselves in caves, great lions might have been heard roaring at night in the forests of the Thames Valley. The bones of this lion have been found in many different parts of England, and a terrible fellow he must have been, for some of his canine teeth (the long sharp teeth in cats and dogs) were more than six inches long. Indeed they were like small swords, and this is why he has been called the “sabre-toothed” lion. There were also bears, like the great grisly bear of America, and leopards, hyenas, and wolves, and besides two kinds of ox far larger than those we have now. But one of the handsomest animals was the great Irish stag. When standing upright the top of his horns would be as high as two tall men. He was indeed a fine fellow with his immense spreading antlers. The deer in our parks would look dwarfs beside him. He inhabited both England and Ireland: but, being found more often in Ireland, he has got the name of the Irish stag. As many as thirty of the skeletons of these stags have been found together under a bog in Ireland, and in some of the bones the marrow is still preserved, and they burn well. Fences have been made of these bones in Ireland, and when the people of a small village in the county of Antrim heard of the battle of Waterloo they made a great bonfire of the bones and horns of the Irish stag to rejoice over the victory. I dare say these stags were hunted by wolves, and perhaps driven on to the ice of ancient lakes, where they broke through and got drowned, for so many of their skeletons are found together. I could not pass this magnificent stag by without giving you a picture of him.[17] He was a much nobler looking animal than the reindeer, which lived along with him at the time in England, and from his appearance I should say he was a swift runner and great fighter. Some antlers have been found locked together, just as these stags died in mortal combat, and I never see Sir Edwin Landseer’s beautiful picture of two red-deer stags fighting without thinking what a grand sight it would have been to see two of these great Irish stags rushing at each other with their powerful horns.

Not one of those animals is living now, and none of them is mentioned in any history or tradition whatever, and though there is no doubt that men living in Europe saw the mammoth alive (as you will find in the next chapter), they knew of no kind of writing in which to tell us of them; these fossils are the only records left, but they speak plainly enough of the time when England and the whole of Europe were inhabited by these races of huge animals.

Now I must carry you away to South America, where there are more wonders. If I were to tell you of all the singular monsters people have found in the beds of the rivers there it would make a book of itself. You know what large rivers there are in that country, and how they run for thousands of miles through almost flat plains called “Pampas.” Well, these rivers have often changed their beds by cutting new channels in the soft soil. The old dry beds of the rivers are the burying-places of some most curious animals, but I have not room to tell you about more than one of them at present. He is called the Megatherium, which means “great beast.” His size and strength were enormous. The largest hippopotamus looks small by his side. His leg bones are bigger than your body. He was more like the sloth than any other living animal, but he could not climb. He stood on those huge, broad hind feet, with his strong tail as a sort of third leg, and tore down the branches of the trees to feed on, or even rooted them up to get at the leaves. Standing by his skeleton in the British Museum[18] one feels quite a shrimp, and he looks strong enough to walk away comfortably with an elephant on his back.

Another immense animal inhabited South America at the time, which geologists have called Dinotherium, or “dreadful beast.”[19] He was a relation of the mastodon, but his tusks were very curious. Instead of being in the upper jaw and turned upwards they stuck out from the lower jaw and curved downwards, giving him a very odd appearance. He most probably had a trunk like the mammoth or mastodon, but perhaps not so long. All these of course were vegetable feeders.

The Tertiary period is so remarkable for the numbers of animals more or less related to elephants and spread all over the world, that we might almost call it the “elephant age,” as the oolite has been named the “reptile age.” These elephantine animals abounded in Europe, Asia, and North and South America, and though none of this kind have yet been found in Australia and Africa, I cannot help thinking they will be discovered in Africa at all events, for there is no doubt that Africa and Europe were once joined.

Australia you know possesses that animal so unlike all others that when we first see it we are quite astonished—the kangaroo. The bones of a huge fossil kangaroo have been found in Australia which must have stood fourteen or fifteen feet high I should think when on its hind legs, or more than twice as large as any living now.[20] Then there were giant birds in New Zealand (something like the ostrich) called dinornis or “dreadful bird.” These fellows had no wings, and they must have been very much taller than the ostrich or emu. To look at their leg bones you would think they were the bones of oxen instead of birds, they are so immensely thick and strong. I do not think any of these are living now, because they have been sought for carefully, and none of the natives even can say that they have seen one. But their skeletons are common in the surface earth, and their bones, cracked to get the marrow out of them, are often dug out of the heaps of refuse collected about ancient cooking places. So that they were used for food, and perhaps they have not been extinct—that is to say, died out—more than a few hundred years; and this is more likely because feathers are sometimes attached to the remains, and undecayed sinews on the feet. A human skeleton has been found in a grave in New Zealand, too, with the egg of one between its arms, and little piles of pebbles are often seen among their bones, where the stomach would be, which the bird swallowed to digest its food, just as many birds do now. The natives called it the Moa, and they have some traditions about it, and, all things considered, it is probably one of the most recent fossil animals, and that is the reason why I have left it to the last.[21]

Now I dare say you will wish to know when the animals living now took the place of those I have described, and which have all passed away. This cannot be told with certainty, but you will see in the “Human Part” that Men were living when the mammoth, mastodon, and some other extinct animals, inhabited the Earth, and that the reindeer, ox, bear, wolf, hyena, &c., have survived to the present day.

Throughout these immense periods of time there are gaps which we cannot yet fill up. No one can yet say, for instance, when the last of the mammoths disappeared, and the first of their near relations, the Indian and African elephants, took their place. These are the missing parts of “the puzzle of life” which you may perhaps one of these days find when you come to study the subject, and when you have learned all that is known at present. But you may be sure of this, that throughout all time there has been progress, the lower forms of animal life have been followed by more perfect forms as the Earth grew older. It is true the lower forms of life have not all died out. These imperfect animals have run through all the ages—the chalk builder of the Cretaceous age lives in the ocean now—and there are many other simple animals which lived in Old Red Sandstone times, and are not extinct yet, but wherever a superior kind of animal has passed away another more perfect has taken its place. This will be seen at once if we compare the “Reptile Age” with the Tertiary. The great ichthyosaurus, plesiosaurus, and pterodactyl are gone, but now we have the more perfect crocodiles and birds. The mammoth is gone, but we have the elephant. There are no giant mosses or towering tree ferns, but our forest trees are more perfect and more varied. The plants which formed the coal forests and once clothed the Earth with beauty have dwindled away to the lowly forms which we must stoop to examine in swamps, and these humble plants are all the surviving relatives of their once noble family. The lordly oaks and elms, stronger, and even more lovely in the sweet drapery of their foliage, and much better fitted for our use, have succeeded all those soft-stemmed plants which grew so fast and were the best possible kind for forming coal.

When you are able to study what is called comparative anatomy you will see how wonderful the plan of creation is, and how beautifully it has been worked out by its great Designer. You will see in the bones of the reptiles of the oolite rocks a prophecy as it were of the birds and animals which were to come. What could be more prophetic of animals with the power of perfect flight than the leather-winged pterodactyl, half lizard and half bird? In some of these animals you will see bones only half formed, and useless to that creature, which were brought to perfection in later times, and became the most important part of the body.

It is very difficult for me to make all this plain to you, but if you are really interested in it you will go to a museum where the fossils are collected, and then I am very much mistaken if you do not find a new and strange world opened to you.