And now there remains the question what enemies besides man these strong-swimming milk-givers can have in their ocean home? We have seen that the orca or killer whale will turn cannibal and devour those of its own kind, and the swordfish is said to attack whales with its formidable spear; but these are not their greatest enemies. With many of the whales it is tiny creatures like those on which they feed which hasten their death, for small parasitic crustaceans cover their head and fins, and feed upon their fat, so that whales which have been infested with these animals are often found to be “dry,” or to have lost nearly all their oil. And thus we see the tables turned, and while the whale feeds upon minute creatures, it is in its turn destroyed by them.

Nevertheless, as a rule, they probably live long lives, till their teeth are worn, or their whalebone frayed and broken, and their blubber wasted away; and then, it may be after eighty or one hundred years of life, they die a natural death. Therefore they probably share with the elephant the longest term of life of any of the warm-blooded animals; and though their existence cannot certainly be said to be an exciting one, yet, when undisturbed by man, it is at least peaceful, sociable, and full of family love.

It may perhaps seem strange that we should have taken these ocean-dwellers last in our glimpses of animal life; but in the first place, how was it possible to show how they are truly related to the land mammalia until we understood the structure of these last? And in the second place, we have as our object to see how the backboned family have won for themselves places in the world, and surely there are none which have done this more successfully or in a more strange and unexpected way than the whales, which, while retaining all the qualities of warm-blooded animals, have won themselves a home in the ocean by imitating the form and habits of fish, and so adapting themselves to find food in the great oceans, where their land relations were powerless to avail themselves of it.

--- WHEN THE COLD HAS PASSED AWAY

CHAPTER XII. A BIRD’S-EYE VIEW OF THE RISE AND PROGRESS OF BACKBONED LIFE.

We have now sketched out, though very roughly, the history of the various branches of the great backboned family, and we have found that, as happens in all families, they have each had their successes and their downfalls, their times of triumph, and their more

sober days, when the remaining descendants have been content to linger on in the byways of life, and take just so much of this world’s good as might fall to their share.

We have seen also that, as in all families of long standing, many branches have become extinct altogether; the great enamel-plated fish, the large armour-covered newts, the flying, swimming, and huge erect-walking reptiles, the toothed and long-tailed birds, the gigantic marsupials, the enormous ground-loving sloths, and many others, have lived out their day and disappeared; their place being filled either by smaller descendants of other branches of the group, or by new forms in the great armies of fish, birds, and milk-givers which now have chiefly possession of the earth.

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.

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