“Moving their feet in a deliberate measure

Over the turf,”

carrying their heavy shell, and eating, when they do eat, in a dull listless kind of way. They do, in truth, live very feebly, for they can only fill their lungs with air by taking it in at the nostrils and swallowing it as frogs do, and then letting it drift out again as the lungs collapse, for their hard shell prevents them from pumping it in and out by the movement of their ribs like other reptiles. This slowness of breathing and the fact that they have only three-chambered hearts like frogs (see p. 76), so that the good and bad blood mix at every round, causes them to be very inactive, and they digest their food very slowly, and have been known to live months and even years without eating.

Fig. 20.

The Greek Tortoise.

This sluggishness would, indeed, certainly be their ruin in a bustling greedy world, if it were not for the strong box in which they live. Take in your hand one of the small Greek[72] or American[73] tortoises, so often sold as pets, and you will see how well he can draw back out of harm’s way, while at

Footnote 72. Testudo Græca.

Footnote 73. Testudo talenlata.

the same time you will, I think, be sorely puzzled to understand how he is made. His head, his four legs, and his tail, with their thick scaly skin, are intelligible enough. But why do all these grow on to the inside of his shell, so that when you trace them up you cannot find the rest of his soft body? You would hardly guess that his shell is the rest of his body, or at least of his skeleton. But it is so. The arched dome which covers his back is made of his backbone and ribs, and the shelly plates arranged over it are his skin hardened into horny shields, which, in the Hawksbill turtle, form the tortoise-shell which is peeled off for our use; while the flat shell under his body is the hardened skin of his belly, and the bones which belong to it.

Fig. 21.

Carapace of the Tortoise.

j, Joints of the backbone grown together; r, ribs formed into a solid cover; sh, shoulder bones; h, hip bones covered by carapace, which has grown over them.

Let us make this clear, for it is a strange history. If you look at the skeleton of a lizard (Fig. 23, p. 103), it is all straight-forward enough. His head fits on to his long-jointed backbone, which is able to bend in all parts freely, down to the very tip of his tail. His front legs with their shoulder bones (s), and his hind legs with their hip bones (h), are attached in their proper places to his backbone, and lastly, his ribs (r) protect the inside of his body, and by expanding and contracting pump the air in and out of his lungs, the front ribs being joined underneath in a breastbone. It is easy to see, therefore, that the lizard may be active and nimble, twisting his body hither and thither, and escaping his enemies by his quickness. But the tortoise is slow and sluggish, and has only managed to baffle the numberless animals which are looking out for a meal by fabricating a strong box to live in. But he had to make this out of the same kind of skeleton as the lizard, with the one difference that he has no breastbone. Let us see how it has been brought about. The bones of his neck are jointed and free enough as you can see (Fig. 21), and so are the joints of his tail, beginning from behind his hip bones (h). But with his back it is different. The backbone can be clearly seen inside the empty shell, running from head to tail so as to cover the nerve-telegraph, but the joints (j) have all grown together, and on the top they have become flattened into hard

plates,[74] while the ribs (r) which are joined to them have also been flattened out and have grown firmly together so as to make an arched cover or carapace. If now you look at the back of the young tortoise (Fig. 22), which has been taken out of the egg before it was full-grown, you will see these plates (p) on the side where the tortoise-shell (ts) has been peeled off. They have not yet widened out enough to be joined together, and the ribs (r) are as yet only united by

Footnote 74. The parts of the joints which flatten out in the tortoise are seen at sp in the lizard and snake, pp. 103, 111.

strong gristle. But what is that row of oblong plates (mp) round the edge? Those are the marginal plates, and they are mere skin bones, like the bony plates of the crocodile, but they are all firmly fixed together so as to bind the edges of the ribs, while plates of the same kind form the shell under the body, and the whole is covered by the horny skin.

Fig. 22.

Back of a Young Tortoise.—(From Rathke.)

ts, Tortoise-shell covering the whole carapace; this has been removed on the right side; mp, marginal plates binding the edges of the ribs; np, neck-plate; p, plates formed of the top of the backbone joints which have grown together; r, ribs which have not yet spread out so as to form a continuous shell; lm, lm′, front and hind leg muscles not yet covered by the carapace.

But there still remains another great puzzle. How come the shoulder bones and hip bones of the tortoise to be inside his ribs instead of being outside them, as in other animals? But look again at our baby tortoise, and you will see that the muscles of his front legs (lm, Fig. 22) are not covered by ribs, neither are those of his hind legs (lm′). They stand just like those of other animals, in front between the ribs and the neck, and behind between the ribs and the tail. But as the tortoise grows up, the bony plates press forwards and backwards, and cover up the shoulders and hips, protecting the soft legs and neck, and giving him the curious appearance of living inside his own backbone and ribs.

In this way, then, the tortoises have managed to hold their own in the world. Living slowly, so that they sometimes go on growing up to eighty years old, wanting but little food, and escaping the cold by sleeping the winter months away in some sheltered nook, they ask but little from Life, while they escape the dangers of sluggishness by growing their skeletons so as to form a citadel which even birds and beasts of prey can rarely break through. They are, it is true, often eaten when young, and the jaguar of Brazil knows how to dig the poor American tortoise out of his shell and eat him; while large birds are formidable enemies to our Greek tortoise, and are said to drop it down on the rocks, and break it to pieces. But, on the whole, they escape most of these dangers, and wander in the woods and dry sandy places of sunny Greece and Palestine, laying their bullet-shaped eggs in warm spots to hatch, seldom wandering far from home, and lying down for their winter’s sleep under heaps of drifted leaves or in holes of the ground.

These are true Land-tortoises,[75] and so are the gigantic tortoises which used to live in the island of Aldabra, and others still surviving in the Galapagos and other islands near Madagascar, which weigh at least 200 pounds, and on whose backs Mr. Darwin rode when he found them travelling up the island to get water to drink, feeding on the juicy cactus as they went. Some carapaces in our museums belonging to these tortoises measure four feet long and three broad; yet they were timid fellows when alive, drawing back completely within their shells when danger was near. We even find some smaller land-tortoises[76] in America, called the Box-tortoises, which have soft joints in their under shell, so that they can draw it up both in front and behind, shutting themselves completely in.

Not so the River-tortoises,[77] which are greedy animal-feeders, and as they live in the water do not need the same protection. Their box is much flatter and more open at the ends, so as to allow them to swim freely with their webbed feet; and they are fierce and bold, the Snapping Turtle[78] of the lakes and

Footnote 75. Testudinea.

Footnote 76. Terrapins.

Footnote 77. Emyx and Trionys.

Footnote 78. Chelydra serpentina.

rivers of America being a terrible fellow, tearing the frogs and fishes in the water with his sharp claws, and even snapping strong sticks in half with his powerful beak. The Mud-tortoises, too, which swim swiftly with their strong legs and long neck outstretched, do not need a hard shell, and they have scarcely any plate below, and only a gristly leathery covering above, which looks very like the mud in which they hide.

Lastly the Sea-tortoises or Turtles, which swim in the warm parts of the Atlantic and Pacific Oceans, have only an open flat shell under which they cannot draw their head and feet, for they strike out boldly into the open ocean, feeding on seaweed, jelly-fish, and cuttle-fish, rowing grandly along with their broad paddles which they feather like oars as they go. They have only one time of weakness—when they come on islands, such as Ascension and the Bahama Islands, which they choose probably because they find fewer large animals there. There the mother turtle arrives at night, looking fearfully around, and if all is still comes flapping in over the sand, and, clearing a hole with her flippers, lays about 200 soft round eggs and covers them up and leaves them. Then in about a month the young turtles come out and make at once for sea, though many of them fall victims to large birds of prey on their way. Woe, too, to the mother when she is laying her eggs, if these large birds are near, for she cannot defend her soft body; or, worse still, if the natives are on the look-out; for then the Green Turtle,[79] coming ashore from the Atlantic, is tilted over on her back and killed for food; and the Hawk’s-bill Turtle[80] from the Indian or Pacific Oceans

Footnote 79. Chelonia midas.

Footnote 80. Chelonia imbricata.

is cruelly stripped of its shell for ornaments. Yet they must run these risks, for their eggs would not hatch without the warm sun, and we see how great is the gap between the last water-breathers and the first air-breathers, when we remember that the frogs go back to lay their eggs in the water, while the tortoises, even when they live far out at sea, are forced to come in to shore, in spite of great dangers, to lay their eggs that their little ones may begin life upon land.

* * * * *

Fig. 23.

Skeleton of a Lizard.

sp, Spinous processes, which in the tortoise are flattened into plates; r, ribs; s, shoulder bone; a, upper arm; e, elbow; fa, forearm; h, hip bone; th, thigh bone; k, knee; l, bones of the leg; q, quadrate bone between upper and lower jaw.

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