Cuvier divided the Linnean genus into two subgenera, _Mustela_ and _Putorius_, the first, Martens and Sables, possessing an additional small premolar on each side of the jaw; the second including the Polecats, Stoats, and Weasels. At a later date Nilsson called these subgenera genera, substituting the name _Martes_ for the Martens and giving that of _Mustela_ to the Weasels. This has the effect of making the name of the Pine Marten, _Martes martes_, which is rather ridiculous; and we have preferred to retain the Linnean name _Mustela martes_. The old spelling of the popular name was Mart_i_n, but in recent works, to avoid any possible confusion with the birds of that name, zoologists have agreed to use _e_ as the second vowel when writing of the mammals. The Pine Marten is found in all the wooded regions of Europe and into Asia; northwards from the Mediterranean to the limits of tree-growth. *Stoat or Ermine* (_Mustela erminea_, Linn.). Though the gun and the snare of the gamekeeper and the poultry-farmer levy their toll upon the Stoat equally with the Polecat, and the keeper's gibbet always shows a goodly row of Stoats, the species manages to keep itself well represented, even in the strictly preserved woods of Southern England. There must, therefore, be some additional reason for the scarcity of the Polecat (see p. 74). The Stoat is much smaller than the Polecat, its total length being only a little more than fourteen inches, of which about four and a half inches are the long-haired but not very bushy tail. In colour, too, it is very distinct, the upper parts being red-brown and the under surface white tinged with yellow. The tail takes the colour of the upper surface, except its tip which is invariably a tuft of long black hairs. In the Alpine districts of Scotland as in other northern countries, the fur in winter becomes pure white all over, with the exception of the tip of the tail which always remains black. This change takes place also in the North of England, but not so generally, and in the South it is only of rare occurrence, and often only partially, some parts remaining brown, as a ring around the eyes producing a spectacled appearance. The summer coloration is "protective" inasmuch that it harmonises generally with the colour of the ground littered with the remains of dead leaves, bark, etc.; but in a landscape under snow for months, as the Alpine districts are, the brown fur would render the animal so conspicuous that it would be heavily handicapped in the hunt for food; but the winter change to white fur enables the Stoat to steal upon its prey unseen from a short distance. The change is quite sudden, given the requisite fall in the temperature, the pigment being withdrawn. (See Introductory chapter.)