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Show 1900.] MUS SYLVATICUS A N D ITS ALLIES. 393 speaking, be regarded as true, although now naturally modified by recent accessions of material, so that I am able to distinguish local forms, for the proper differentiation of which, although I believe them to be perfectly recognizable and distinct, there was needed the accumulation of a considerable number of specimens. Mus sylvaticus appears in fact to be a form which, in its longstanding and successful struggle for existence, has attained to a height of specialization from which it has either very little power of variation, or else which is such as to fulfil all the needs of the species iu almost any conditions with which it may be brought into contact. The possible range of its variations, whether individual or geographical, w7ould seem to be narrow. Within this narrow range, however, variation is very evident and perplexing. The animal, indeed, while apparently having small power of varying, uses to the utmost the power which it possesses. Unlike some of our common mammals, such as the Squirrel, Babbit, or Bat, it is not subject to either melanism or albinism. In the whole series of the ' Zoologist' and the volumes of tbe ' Field'for the last twenty years, there is not to be found a single recorded instance of a well-marked sport of this species-a result which would have been very widely different had the object of the search been Sciurus vulgaris, Talpa europcea, or Mus musculus. This, of course, does not prove that conspicuous sports do not occur, but it undoubtedly emphasizes their rarity l. I have not thought it worth while to supplement this result by a search for information, all of which would probably be of a highly negative character, through any number of the works of foreign writers; but neither in those of Bell2 nor of J. H . Blasius 3 can any allusion to such sports be found. Dehne 4, however, mentions a variety, which he calls " die isabellfarbige Waldmaus," and which he characterizes as very rare, since he had only seen one example, and that in the summer of 1833 in the district of Penig. He had never seen white or otherwise coloured varieties. De Selys-Longchamps ° records an " Isabelle albine" variety with pink eyes, and states that such occur " tres accidentellement." Similar isabelline, white, or white-speckled varieties are noted as of extremely accidental occurrence by Bonaparte 6, Fischer7, and Mina Palumbo 8. 31us sylvaticus is then, it seems, a good instance in support of Mr. A. Sedgwick's remarks 9 on the loss of variability in an old species. 1 It must not be forgotten also that sports of Mus sylvaticus may have been occasionally credited to Mus musculus. 2 ' British Quadrupeds,' ed. 2 (1874). 3 ' Saugethiere Deutschlands,' 1857. 4 AUgem. deut, naturh. Zeit. 1858, pp. 182-3. 5 ' Etudes de Micromammalogie,' 1839, p. 65. 6 ' Fauna Italica,' 1832-1841, art. on Mus sylvaticus. 7 " Saugethiere des St. Petersburger Gouverneiuents," Der Zoologische Garten 1869, p. 340. 8 Cat.dei M a m m . della Sicilia, 1868, p. 72. See E.Cantoni's " Elenco Generale dei Mammiferi soggetti ad albinismo," in Atti della Soc. Ital. di Sci. Nat. vol. xxiii., 1880. a Presidential Address to Section D of British Association : Dover, 1899. |