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Show CHAP. IV.] EVOLUTION THE KEY TO DISTRIBUTION. o5 species, E. passeTina, which ranges eastwards to the Lena river, and in winter as far south as Amoy in China; but in Japan the original species appears again, receiving a new name (E. ?Yr'rhulina), but Mr. Scebohm assures us that it is quite !~distinguishable from the European bird.1 Although the distance between these two portions of the species is not so great as in the last example, being about 2,000 miles, in other respects the case is a most satisfactory one, because the forms which occupy the intervening space are recognised by Mr. Seebohm himself as undoubted species. The European and J apanese Jays.-Another case somewhat resembling that of the marsh tit is afforded by the European and Japanese jays (GaT?"·uhts glanda?"itts and G. japonicus). Our common jay inhabits the whole of Europe except the extreme north, but is not known to extend anywhere into Asia, where it is represented by several quite distinct species. (See Map, Frontispiece.) But the great central island of Japan is inhabited by a jay (G. japonicus) which is very like ours, and was formerly classed as a sub-species only, in which case our jay would be considered to have a discontinuous distribution. But the specific distinctness of the Japanese bird is now universally admitted, and it is certainly a very remarkable fact that among the twelve species of jays which together range over all temperate Europe and Asia, one which is so closely allied to our English bird should be found at the remotest possible point from it. Looking at the map exhibiting the distribution of the several species, we can hardly avoid the conclusion that a bird very like our jay once occupied the whole area of the genus, that in various parts of Asia it became gradually modified into a variety of distinct species in the manner already explained, a remnant of the original type being preserved almost unchanged in Japan, owing probably to favourable conditions of climate and protection from competing forms. Supposed Exarnples of Discontinuity arnong NoTtk A me?"ican BiTds.-In North America the eastern and western provinces are so different in climate and vegetation, and are besides separated by such remarkable physical barriers-the arid 1 lbis, 1879, p. 40. l!' |