This happened on a mild, damp day in November 1873, and after that I saw the tube in ‘several snakes,’ but I regret the names were not entered in my notebook at the time. In the smaller non-venomous snakes, or in the lacertines—of which there were then a large number—I do not remember to have observed it. They despatch their frog or mouse so quickly that they would scarcely need a fresh supply of air meanwhile. In the larger vipers, rattlesnakes, and constrictors, the air-tube was undoubtedly witnessed. Winter then terminated my observations, and afterwards a prolonged absence from town. Unfortunately, when observations were about to be resumed, the change of the plans at the Zoological Gardens, and the exclusion of the public, defeated my intentions, though on one occasion I did see the windpipe of little _Natrix torquata_ very distinctly; and this was the smallest snake in which I had ever observed it. _Natrix_ had nearly disposed of a large frog. The whole of it was in his mouth, which was widely expanded, and the air-tube was protruded sideways, not _out_ of the mouth, but sufficiently forward to enable one to distinguish its form, and the action of the _petite languette_. The prey being unusually large, the snake had needed air while swallowing it. On several occasions in snakes recently dead, and of various sizes, one has been able to notice how admirably this tube, which lies along the mouth like a soft cushion, somewhat in the form of a parrot’s tongue, is supplied with space in the roof, arched to fit it, the palate teeth enclosing it on each side, while the opening, or glottis, exactly meets the nostrils, _les arrières nez_, bringing it into communication with the outer air. In a little _Coluber_, just dead, I again had an opportunity of making observations. The membranous coating was so thin and transparent that the rings of the windpipe could be very distinctly traced from a quite forward position in the mouth, and beginning on and over the tongue sheath. The surrounding skin or membrane was also loose and abundant, so that with the point of a needle the upper part of the windpipe could be easily drawn forward _beyond_ the lips. In life the little snake could thus have voluntarily protruded it as occasion required.