chap, iv.] EVOLUTION THE KEY TO DISTRIBUTION. 
65 
species, E. passerina, 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 . 
pyrrhulina), but Mr. Seebohm assures us that it is quite 
indistinguishable 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 Japanese Jays . — Another case somewhat 
resembling that of the marsh tit is afforded by the European 
and Japanese jays ( Garrulus glandarius 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 in- 
habited 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 Examples of Discontinuity among North American 
Birds.— 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 Ibis, 1879, p. 40. 
F 
