perfect and unreversed through its entire length. Both sloughs have been preserved. As a more general rule the slough is reversed; but in the process it folds back and over the body, _outside_ of it, in the manner of a stocking drawn off from knee-wards, and turning back till entirely reversed it leaves the foot. This common and apt illustration is easily understood if we suppose the top of the stocking to be the mouth of the slough, and the toe its tail. But as the toes might sometimes slip out of a stocking when nearly off, so does the tail of a snake sometimes slip out; this portion therefore is often found _unreversed_. More than a hundred years ago the sloughing of snakes was understood and described in the _Phil. Trans._ for 1747, vol. xl.; as also of lizards ‘slipping off their skins as vipers do.’ Some young vipers changed at six weeks old, and again in two months after that. ‘They always began at the mouth,’ said the writer. The process has been witnessed and described by many since that, though more by foreign than by English naturalists. Some of the older writers have told us that ‘a snake frequents the spot where it has cast its skin,’ or, in other words, that it selects that locality for its nest—a fact as curiously stated as if you related of a person that he chose for his home the house in which he performed his toilet. Snakes have a strong affection for locality; and where their nest is, there, or near it, their garments are naturally renewed. Another mooted question has been the precise period of sloughing; formerly the accepted opinion was that once a year, viz. in the spring, was the usual habit. This was probably from so many coils of skins being found at this season. That they do change in the spring may be established as an almost invariable rule; but not then only. No precise periods can be given with certainty, because it depends on the individual, its health and surroundings. The ophidian is a fastidious creature, and when his garment becomes soiled or uncomfortable he discards it. Thus after hibernation, when for some months numbers of snakes have been coiled in masses in a cave or under stones and rubbish, and they emerge into daylight, aroused by the sun’s revivifying rays, what more natural than to cast off the old winter garb for a more comfortable suit?