The Stoat, or Ermine, is an important species closely allied to the Weasel, from which it differs chiefly by its greater size, and by the peculiarities of its colouring. In summer the upper parts vary from yellowish-brown to mahogany brown, while the under side is white tinged with sulphur-yellow, except on the throat, which is pure white. The tail is tipped with black. The brown upper and white under surfaces are separated by a perfectly distinct line of demarcation, which extends from the snout to the root of the tail, dipping down at the limbs, so as to include the outer surfaces of the latter in the dark area. In winter, on the other hand, the skin is, with the exception of the tip of the tail, which always remains black, pure white, tinged here and there with sulphur-yellow. Intermediate states between full winter dress and full summer dress are often found, and these, curiously enough, show their half-way character in two ways. Sometimes there is an alteration in level of the line of demarcation between the white and brown portions of the skin, the latter being occasionally found restricted to a narrow strip along the back, but remaining still without any admixture of white hairs. In other cases, again, the line of demarcation remains unaltered, but the dark portions become gradually lighter and lighter, until the final white dress is assumed. As to the interesting question of the exact manner and cause of this change, it is sometimes stated that the direct influence of cold produces a rapid lightening in the colour of individual hairs, while there are also facts to show that the change is not due to an alteration in colour of existing hairs, but to a renewal of the coat, the hairs of one colour being replaced by those of the other. Dr. Elliott Coues, who has worked up the subject in an able and exhaustive manner, has satisfied himself that the change may take place in either way. Some of his specimens, “notably those taken in spring, show the long woolly white coat of winter in most places, and in others present patches--generally a streak along the back--of shorter, coarser, thinner hair, evidently of the new spring coat, wholly dark-brown. Other specimens, notably autumnal ones, demonstrate the turning to white of existing hairs, these being white at the roots for a varying distance, and tipped with brown. These are simple facts not open to question. We may safely conclude that if the requisite temperature be experienced at the periods of renewal of the coat, the new hairs will come out of the opposite colour; if not, they will appear of the same colour, and afterwards change; that is, the change may or may not be coincident with shedding. That it ordinarily is not so coincident seems shown by the greater number of specimens in which we observe white hairs brown-tipped. As Mr. Bell contends, temperature is the immediate controlling agent. This is amply proven in the fact that the northern