At the risk of being tedious, a few more words must be added on this subject of progression, because we so constantly see it asserted that snakes ‘move with difficulty over smooth surfaces.’ Their actions have not excited sufficient attention and study. Have you ever watched them moving about in their bath at the Zoological Gardens? The motions of a python once particularly struck me. The earthenware pan was smooth polished ware, and with enough water in it to render it smoother, if that be possible. The reptile was not swimming, for the thicker part of its body was not even wholly submersed. The pan was too shallow for that, and too small to permit of any portion of the python being fully extended. It moved in ever-varying coils and curves, yet with the greatest ease, its head slightly raised, so that the nostrils and mouth were out of water. It seemed to be enjoying its bath, as it actively glided, turned, and curved in that wonderful fashion which Ruskin described as ‘a bit one way, a bit another, and some of him not at all.’ There could be no hold for the scutæ in this case, nor could I detect any action of the ribs as in crawling over a less smooth surface. The creature seemed to move by its easy sinuations, and with no more effort than you see in the fish at an aquarium. Perfectly incomprehensible is this lax and leisurely movement in shallow water. Even the inert little slow-worm astonishes us by its physical achievements, which will be duly described in its especial chapter. But among the most characteristically active are the small and slender tree snakes, the _Dryadidæ_ and _Dendrophidæ_, mostly of a brilliant green. These and the Whip snakes are exceedingly long and slender, the tails of many of them very gradually diminishing to a fine and attenuated point. Some of them are closely allied to the lizards, and skim and dash through the foliage with a scarcely perceptible weight. These are the true acrobats, full of gracile ease and activity. Many are over four feet in length, and not much thicker than a pencil. They are found in the hot countries of both hemispheres. The Siamese call some of them ‘sunbeams,’ from their combination of grace and splendour, and in Brazil some have the brilliant tints of the humming-birds. These little creatures in your hand feel like soft, fine, satin cords endowed with life. Dr. Wucherer, writing from Brazil, enthusiastically declared that he was always delighted to find one of them in his garden. He discovered them coiled in a bird’s nest, their body of two feet long occupying a space no larger than the hollow of your hand. ‘In an instant they dart upwards between the branches and over the leaves, which scarcely bend beneath their weight. A moment more, and you have lost them.’[70]