And now, if we leave the tortoises and turn to the Lizards, we find them meeting life’s difficulties in quite a different way. Here are no sluggish movements, horny beaks, and strong boxes; but bright-eyed creatures covered with shining scales, their mouths filled with sharp teeth, with which even the small lizards can bite fiercely, and having nimble lissome bodies, which wriggle through the grass or up the trees in the twinkling of an eye. Yet the lizards, as we have seen, are formed on the same plan as the tortoise, and their scales are thickenings in their outer skin, just as his tortoise-shell is, and not true scales like those of fish. They have learned to hold their own by sharpness and quickness, and are probably the most intelligent of all the cold-blooded animals, though even they are only lively in a jerky way under the influence of warmth. They can breathe more easily than the tortoise, for their ribs rise and fall, drawing in and driving out the air they need; but they are still cold-blooded, for their heart has only three chambers. It is when the bright sun is shining that they love to dart about, chasing the insects upon which they feed; and the joints of their backbone move so easily upon each other that they can twist and turn in all imaginable ways, keeping their heads twisted in a most comical manner when on the watch for flies. Nay, the very vertebræ themselves are so loosely made that they can split in half, and if you seize a lizard by the tail he will most likely leave it in your hand and grow another. They can live both in dry sandy places, where larger animals cannot find food and water, and in thick underwood, and marshy unhealthy places, where more quickly-breathing animals would be poisoned by the fetid air; and we find them swarming in hot countries in spite of enemies, their scales protecting them from the rough surface of the rocks and trees on which they glide, their feeble legs scarcely ever lifting their body from the object on which they glide rather than walk. [Illustration: Fig. 24. Gecko and Chamæleon.]