The hold which the ventral scales have of the ground obviously renders it easier for the reptiles to pass over a rough than a smooth surface; what are obstacles to other creatures are facilities to them. But they appear to be never at a loss. On a boarded room, or even a marble floor, they will manage progression of some sort,—many by the pressure of the tail to push themselves forward, and others with an action that can be compared only with swimming. With the same rapid, undulating motion as swimming, the active snakes skim through the grass, or over soft herbage, on which they seem to make no impression. Their swift sinuations are almost invisible to the eye. You only know that a snake _was_ there, and now has vanished. The ‘Rat’ snake of Ceylon (_Ptyas mucosus_) (see frontispiece) and the ‘Pilot’ snakes of America are among the best known of these swift-flitting or gliding creatures. Rats are fleet little quadrupeds, but their enemies, the Rat snakes of India, are more than their match. Sir Emerson Tennant, in his _History of Ceylon_, describes an encounter with one. _Ptyas mucosus_ caught a rat, and both captor and captive were promptly covered with a glass shade to be watched. With an instinct to escape stronger than hunger, _Ptyas_ relinquished his hold, and manifested uneasiness. Then the glass shade was raised a trifle, and instantly away ran the rat; but the snake was after it like a flash, caught it, and glided away swiftly, with head erect and the rat in its mouth. At one of the Davis lectures at the Zoological Gardens, a fine Rat snake in the Society’s collection was exhibited, and was permitted to be handled by a favoured few. To hold it _still_ was not possible, for the creature glided through the hand, and entwined itself about one as if a dozen snakes had you in possession. It was very tame, and accustomed to be handled by the keeper, whose especial pet it was; otherwise _Ptyas_ is a powerful snake, and quite capable of strangling you should it take a fancy to constrict your neck. On another occasion this same snake constricted my arm sufficiently to make my fingers swell; but that was not so much in anger as for safety, because it did not like to be fettered in its movements, or to be somewhat unceremoniously examined. A younger and less tame specimen tried to bite me, and squeezed my fingers blue by constricting them. There is no circumventing these ‘lithe and elegant beings.’ They will get into your pocket, or up your sleeve; and while you think you have the head safely in your hand, the whole twelve feet of snake will have glided through, and be making its way to the book shelves, or where you least expect to see it.