Still, on the whole, the history has been one of a gradual rise from lower to higher forms of life; and if we put aside for a moment all details, and, forgetting the enormous lapse of time required, allow the shifting scene to pass like a panorama before us, we shall have a grand view indeed of the progress of the great backboned family.

First, passing by that long series of geological formations in which no remains of life have been found, or only those of boneless or invertebrate animals, we find ourselves in a sea abounding in stone-lilies and huge crustaceans,[190] having among them the small forms of the earliest fish known to us, those having gristly skeletons. Then as the scene passes on, and forests clothe the land, we behold the descendants of these small fish becoming large and

Footnote 190. Picture heading, Chap. II.

important, wearing heavy enamelled plates or sharp defensive spines; some of them with enormous jaws, two or three feet in length, wandering in the swamps and muddy water, and using their air-bladder as a lung. But these did not turn their air-breathing discovery to account; they remained in the water, and their descendants are fish down to the present day.

It is in the next scene, when already the age of the huge extinct fishes is beginning to pass away, and tree ferns and coal forest plants are flourishing luxuriantly, that we find the first land animals,[191] which have been growing up side by side with the fish, and gradually learning to undergo a change, marvellous indeed, yet similar to one which goes on under our eyes each year in every country pond. For now, mingling with the fish, we behold an altogether new type of creatures which, beginning life as water-breathers, learn to come out upon the land and live as air-breathers in the swamps of the coal forests.

A marvellous change this is, as we can judge by watching our common tadpole, and seeing how during its youth its whole breathing organs are remade on a totally different principle, its heart is remodelled from an organ of two chambers into one of three, the whole course of its blood is altered, some channels being destroyed and others multiplied and enlarged, a sucking mouth is converted into a gaping bony jaw, and legs with all their bones and joints are produced where none were before, while the fish’s tail, its office abandoned, is gradually absorbed and lost.

The only reason why this completely new creation, taking place in one and the same animal, does

Footnote 191. Picture heading, Chap. IV.

not fill us with wonder is, that it goes on in the water where generally we do not see it, and because the most wonderful changes are worked out inside the tadpole, and are only understood by physiologists. But in truth the real alteration in bodily structure is much greater than if a seal could be changed into a monkey.

Now this complete development which the tadpole goes through in one summer is, after all, but a rapid repetition, as it were, of that slow and gradual development which must have taken place in past ages, when water-breathing animals first became adapted to air-breathing. Any one, therefore, who will take the spawn of a frog from a pond, and watch it through all its stages, may rehearse for himself that marvellous chapter in the history of the growth and development of higher life.

And he will gain much by this study, for all nature teaches us that this is the mode in which the Great Power works. Not “in the whirlwind,” or by sudden and violent new creations, but by the “still small voice” of gentle and gradual change, ordering so the laws of being that each part shall model and remodel itself as occasion requires. Could we but see the whole, we should surely bend in reverence and awe before a scheme so grand, so immutable, so irresistible in its action, and yet so still, so silent, and so imperceptible, because everywhere and always at work. Even now to those who study nature, broken and partial as their knowledge must be, it is incomprehensible how men can seek and long for marvels of spasmodic power, when there lies before them the greatest proof of a mighty wisdom in an all-embracing and never-wavering scheme, the scope of which is indeed beyond our intelligence, but the partial working of which is daily shown before our very eyes.

But to return to our shifting scene where the dense forests of the Coal Period next come before us. There, while numerous fish, small and great, fill the waters, huge Newts have begun their reign (Labyrinthodonts), wandering in the marshy swamps or swimming in the pools, while smaller forms run about among the trees, or, snake-like in form, wriggle among the ferns and mosses; and one and all of these lead the double-breathing or amphibian life.

In the next scene the coal forests are passing away, though still the strange forms of the trees and the gigantic ferns tell us we have not left them quite behind; and now upon the land are true air-breathers,[192] no longer beginning life in the water, but born alive, as the young ones of the black salamander are now (see p. 81). The Reptiles have begun their reign, and they show that, though still cold-blooded animals, they have entered upon a successful line of life, for they increase in size and number till the world is filled with them.

Meanwhile other remarkable forms now appear leading off to two new branches of backboned life. On the one hand, little insect-eating warm-blooded marsupials scamper through the woods, having started we scarcely yet know when or where, except that we learn from their structure that they probably branched off from the amphibians in quite a different line from the reptiles, and certainly gained a footing upon the earth in very early times. On the other hand, birds come upon the scene having teeth in their

Footnote 192. Picture heading, Chap. VIII.

mouths,[193] long-jointed tails,[194] and many other reptilian characters. We have indeed far more clue to the relationship of the birds than we have of the marsupials, for while we have these reptile-like birds, we have also the bird-like reptiles such as the little Compsognathus, which hopped on two feet, had a long neck, bird-like head and many other bird-like characters, though no wings or feathers.

The birds, however, even though reptile-like in their beginning, must soon have branched out on a completely new line. They for the first time among this group of animals,[195] have the perfect four-chambered heart with its quick circulation and warm blood; while not only do they use their fore limbs for flying (for this some reptiles did before them), but they use them in quite a new fashion, putting forth a clothing of feathers of wondrous beauty and construction, and with true wings taking possession of the air, where from this time their history is one of continued success.

And now we have before us all the great groups of the backboned family—fish, amphibia, reptiles, birds and mammalia; but in what strange proportions! As the scenery of the Chalk Period with its fan-palms and pines comes before us, we find that the gristly fish, except the sharks and a few solitary types, are fast dying out, while the bony fish[196] are but just beginning their career. The large amphibians are all gone long ago; they have run their race, enjoyed their life and finished their course, leaving only the small newts and salamanders, and later on

Footnote 193. Picture heading, Chap. VI.

Footnote 194. Ibid. Chap. VII.

Footnote 195. Sauropsida.

Footnote 196. Picture heading, Chap. III.

the frogs and toads, to keep up the traditions of the race. The land-birds are still in their earliest stage; they have probably scarcely lost their lizard-like tail, and have not yet perfected their horny beak, but are only feeling their way as conquerors of the air. And as for the milk-givers, though we have met with them in small early forms, yet now for a time we lose sight of them again altogether.

It is the reptiles—the cold-blooded monster reptiles—which seem at this time to be carrying all before them. We find them everywhere—in the water, with paddles for swimming; in the air, with membranes for flying; on the land hopping or running on their hind feet. From small creatures not bigger than two feet high, to huge monsters thirty feet in height, feeding on the tops of trees which our giraffes and elephants could not reach, they fill the land; while flesh-eating reptiles, quite their match in size and strength, prey upon them as lions and tigers do upon the grass-feeders now.[197] This is no fancy picture, for in our museums, and especially in Professor Marsh’s wonderful collection in Yale Museum in America, you may see the skeletons of these large reptiles, and build them up again in imagination as they stood in those ancient days when they looked down upon the primitive birds and tiny marsupials, little dreaming that their own race, then so powerful, would dwindle away, while these were to take possession in their stead.

And now in our series of changing scenes comes all at once that strange blank which we hope one day to fill up; and when we look again the large

Footnote 197. Picture heading, Chap. V.

reptiles are gone, the birds are spreading far and wide, and we come upon those early and primitive forms of insect-eaters, gnawers, monkeys, grass-feeders, and large flesh-eaters, whose descendants, together with those of the earlier marsupials, are henceforward to spread over the earth. We need scarcely carry our pictures much farther. We have seen how, in these early times, the flesh-feeders and grass-feeders were far less perfectly fitted for their lives than they are now;[198] how the horse has only gradually acquired his elegant form; the stag his branching antlers; and the cat tribe their scissor-like teeth, powerful jaws, and muscular limbs; while the same history of gradual improvement applies to nearly all the many forms of milk-givers.

But there is another kind of change which we must not forget, which has been going on all through this long history, namely, alterations in the level and shape of the continents and islands, as coasts have been worn away in some places and raised up or added to in others, so that different countries have been separated from or joined to each other. Thus Australia, now standing alone, with its curious animal life, must at some very distant time have been joined to the mainland of Asia, from which it received its low forms of milk-givers, and since then, having become separated from the great battlefield of the Eastern Continent, has been keeping for us, as it were in a natural isolated zoological garden, the strange primitive Platypus and Echidna, and Marsupials of all kinds and habits.

So too, Africa, no doubt for a long time cut off

Footnote 198. Picture heading, Chap. IX.

by a wide sea which prevented the larger and fiercer animals from entering it, harboured the large wingless ostriches, the gentle lemurs, the chattering monkeys, the scaly manis, and a whole host of insect-eaters; while South America, also standing alone, gave the sloths and armadilloes, the ant-bears, opossums, monkeys, rheas, and a number of other forms, the chance of establishing themselves firmly before stronger enemies came to molest them. These are only a few striking examples which help us to see how, if we could only trace them out, there are reasons to be found why each animal or group of animals now lives where we find it, and has escaped destruction in one part of the world when it has altogether disappeared in others.

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