All these groups are very distinct now, and we naturally turn back to ancient times to ask how they first started each upon their own road. But when we do this, we meet with a history so strange that it makes us long to open the great book of Nature still further, and by ransacking the crust of the earth in all countries to try and find the explanation, which will no doubt come some day to patient explorers. The history is this. We saw in the last chapter that in those far distant ages, when even reptiles were only beginning to spread and multiply by land and sea, and when, although birds probably existed, still they did not as yet leave any traces behind, small milk-giving and insect-eating animals, the Microlestes and Dromatherium (see p. 183), were already living upon the earth, and left their teeth and jaws in the ground.

Now, as ages passed on and the reptiles increased in strength, these little milk-giving animals evidently flourished, for though we have not yet discovered any of their bones in the rocks of the Chalk Period, yet as we find them both before and after that time, they must have lived on in some part of the world, the rich vegetation and abundant insect life affording them plenty of food. Meanwhile the huge reptiles, of kinds now long extinct, reigned over land and sea and air, and were in the height of their glory,—when suddenly there comes a blank and their history ends. When we look again, “a change has come o’er the spirit of the dream,” and in the next period we find their bones no more. From that time we meet only with the four groups of lizards, snakes, tortoises, and crocodiles, which still survive; and the place of the swimming, flying, and walking reptiles is taken by four-footed and milk-giving animals.

Some of these were still marsupials like those that had gone before; others were of strange forms, distantly related to them; others were curious ancestral forms of our hyænas and bears, dogs and civets, horses and tapirs,[129] in which the characters which distinguish these groups were not so distinct as they are now, while others again were old forms of moles, hedgehogs, squirrels, bats, and lemurs. In what part of the world, then, had all these been growing up, that we come upon them so suddenly? Before the seas of the chalk only the small marsupials; after them, when the areas of land began to increase in extent, a whole army of milk-givers, so different from each other and so well adapted for their lives, that we even find among them such peculiar forms as whales, with their arms converted into paddles, and bats with their arms acting as wings.

What an idea this gives us of the immense period of time that must have elapsed while the chalk was forming, the reptiles becoming extinct, and the mammalia taking their place!

We have had a hint of this before, when we

Footnote 129. For a few of these forms see the picture-heading, p. 209.

learned in Life and her Children how infinitely minute the shells are of which chalk is made, and what enormous thicknesses remain of the chalk-beds. And now we find these facts strengthened by the great changes which then took place in the animal world, for even if (as is likely) older forms of these large milk-givers existed in earlier times, and we have not yet found them, yet there are such great differences between whales, bats, dogs, and lemurs, that our imagination stands appalled at the time required to account for them.

Again, where are the traces of all the forms which must have existed between the little marsupials and this great army of four-footed beasts? At present no one can answer. Forty years ago we knew nothing even of those early marsupials, and people said there were no milk-giving animals until after the time when the chalk was formed. Now a few jaws have told us that milk-givers had been already in the world for ages; and it may be that before forty years more have passed, some child now reading these lines, and following in the footsteps of such patient explorers as Beckles and Gaudry, or the American naturalists Leidy, Cope, Marsh and others, who have such a grand field before them, may discover bones which will unravel the history of that crowd of mammalia which now seems to start up like Cadmus’ army from the ground.

But for the present we can only begin with them as we find them immediately after the Chalk Period, and a strange motley group they appear. There, roaming among the palms, evergreens, screw-pines and tree-ferns, which flourished in Europe and North America in those warmer times, were beasts larger than oxen, with teeth partly like the tapir, partly like the bear, and feet like the elephant,[130] which may have been both animal and vegetable feeders. With them were true vegetarians, which could be called neither rhinoceroses, horses, nor tapirs, but had some likeness to each.[131] Others, half-pigs half-antelopes, were thick-skinned, but graceful and two-toed,[132] while a little fellow no bigger than a fox,[133] with five toes on his front feet and three behind, the ancestor of our horses, grazed in the open plains. There too, moles, hedgehogs, and dormice had already begun to make their underground homes, and squirrels and lemurs sprang about the trees of the forest, where bats roamed at night in search of insects. Nor was this life without its dangers, for beasts of prey, half-bears half-hyænas,[134] were there to feed upon their neighbours, and with them a creature half-dog half-civet,[135] with several other carnivorous animals with feeble brains and partly marsupial characters,[136] and lastly a large flat-footed dog-bear,[137] something between a dog, a cat, and a bear, with a very small brain but plenty of teeth, represented the most primitive flesh-eating animal known to us.

None of these forms were of the same species as those now living, and many of them, as we see, had characters which we now find in two or three different animals; showing that they had not yet specialised the various weapons of attack and defence, and the

Footnote 130. Coryphodon.

Footnote 131. Paleotherium and Anoplotherium.

Footnote 132. Xiphodon.

Footnote 133. Eohippus.

Footnote 134. Hyænarctos.

Footnote 135. Cynodon.

Footnote 136. Hyænodon and others.

Footnote 137. Arctocyon.

difference of limbs and teeth which now distinguish their descendants. So that, for example, though there were fierce animals of prey, none had yet the formidable teeth of the tiger nor the muscular strength of the lion, neither had the vegetarians the fleetness of the horse, the horns of the deer, nor the large brain of the elephant.

This had all to come with time, and from that day to this their descendants have been spreading over the earth. Some, large and powerful, have conquered by strength; some, by superior intelligence, have learned to herd together and protect each other in the battle of life; some have gone back to the water and imitated the fish in their ocean home; and others, smaller and feebler, have lived on by means of their insignificance, their rapid multiplication, and their power of hiding, and feeding on prey too minute to attract their more powerful neighbours.

Among all these there are hundreds of different forms, branching out here and there, crossing each other’s path and often jostling on the way; while during the long period between our first knowledge of them and now, they have been driven or have travelled from one country to another, from the northern to the southern hemisphere, or from the Old to the New World, till in many cases it is impossible to say what routes they have taken.

How, then, shall we get a glimpse of the nature of these large groups? Shall we take the moles and hedgehogs as the lowest, and the monkeys as the highest, and then travel in a straight line through the forms between? Scarcely, I think, for it is very doubtful whether the lemur and the dormouse may not be able to boast of ancestors as ancient as the moles, while the elephant and the dog are surely as intelligent and far nobler animals than the monkey. No! we must make up our minds at once that the different branches have grown side by side to much the same height, so that our genealogical tree, if it were possible to make one, would, like a real tree, be a mass of entangled twigs, some of which would, indeed, be less aspiring than others, yet on the whole we could scarcely say that one reached nearer to the sky than another. What perfection they have each obtained in their own line is quite another question, and one which we are able to trace out.

* * * * *

Thus, for example, the gnawing animals or Rodents, and the insect-eaters or Insectivores, are undoubtedly the lowest types next to the sloths and armadilloes, the insect-eaters especially having very primitive skeletons and small brains. Yet we shall find that we pass very naturally from them to the intelligent monkeys, while, on the other hand, the vegetable-feeders and flesh-eaters go off upon quite a different line of their own.

Let us, then, begin with these two lowly groups, the Rodents and Insectivores, and see how they have conquered their humble place in the world. One thing is clear, that they do not hold it by strength or audacity, for taken as a whole they are small and weak animals; the giants among rodents, the Capybaras of South America, where all lower kinds of animals thrive, are only as large as good-sized pigs, and the smallest, the “Pocket-mice” of North America, are not bigger than large locusts; while the insect-eaters have nothing larger than the “Tenrecs” or soft-bristled hedgehogs of Madagascar, about the size of a tailless cat; and the rest of the group vary from two to eight inches all over the world. Moreover, they are as a rule timid, and though some of them fight fiercely among themselves, yet they scamper away and hide at the least alarm, and generally choose the twilight or the dark night for their feeding time.

Stroll out some fine summer’s evening, when the sun has set and the moon has not yet risen, and as you wander in the fields and woods with eye and ear open, you will scarcely have gone far before you will be aware that there is plenty of stir going on. Some active little field-mouse will cross your path in her eager search for grain and seeds to lay up for her winter store, or you may startle a hare in the long grass and watch her run across the field, or see her sit upright on her haunches surveying the quiet night-world. Or, if you pass over a common, the number of little white tips glancing in the twilight from under the furze bushes will tell you that the rabbits have not yet disappeared into their burrows; while as you enter the wood the sharp little eyes of the squirrel will peep down upon you from the beech trees, as she watches over her little ones in their comfortable nest in the branches.

All these are Rodents, and you may know them by their four long chisel-like front teeth (see B, Fig. 55), which have a large gap on each side, between them and the grinding teeth behind. These chisel teeth have not bony roots like the teeth of most animals, but rest in a deep socket, and continue growing during the whole of the animal’s life; and they have a hard coat of enamel in front, so that as the tooth wears away behind, this enamel stands out and forms a sharp cutting edge, and there is perhaps no tool more efficient for gnawing a root, a nutshell, or the solid wood of a tree, than the tooth of a beaver or rat.

Page 28 of 47