Page:Natural History, Reptiles.djvu/76

68 through which they pass. A comparison of the progression of these, however, and even of the Slow-worm, with that of the true Snakes, will show that the latter only employ the free termination of their ribs as organs of locomotion. In these the ribs serve absolutely and perfectly the function of feet, and with the exception of their being covered with integument, their action is exactly that of the multitudinous feet in the Scolopendra or Julus, the whole series of ribs coming into contact in succession. At the same time, it is upon the lateral pressure of successive portions of it, that the Serpents mainly depend for the rapidity of their progression."

The Sauria are, we believe, exclusively land-animals, none of them being fitted for inhabiting the water, though some are able to swim, in emergency. Most of them are terrestrial, but not a few are arboreal, more or less entirely, from the Chameleon, which, with his opposible toes, climbs about the branches of trees, to the little Anoles, which run about the trunks and leap from leaf to leaf; and some, as the Geckos, inhabit the crevices of old buildings, among the rafters of which they crawl in all positions, frequently with the back downward. These last are rather slow in their motions, and the Chameleons are still more deliberate; but the characteristic of the Order is extreme agility, and some of the ground Lizards dart to and fro, and skim the surface of the earth with the rapidity of a bird. In one genus, Draco, the skin of the sides is stretched upon a prolongation of the ribs, and acts as a parachute, or as the