38 
ISLAND LIFE. 
[part I. 
We find, that out of a total of 118 British Passeres there are: 
32 species which range to North Africa and Central or 
East Asia. 
25 species which range to Central or East Asia, but not 
to North Africa. 
43 species which range to North Africa and Western Asia. 
6 species which range to North Africa, but not at all into 
Asia. 
6 species which range to West Asia, but not to North Africa. 
6 species which do not range out of Europe. 
These figures agree essentially with those furnished by the 
mammalia, and complete the demonstration that all the tem- 
perate portions of Asia and North Africa must be added to Europe 
to form a natural zoological division of the earth. We must also 
note how comparatively few of these overpass the limits thus 
indicated ; only seven species extending their range occasionally 
into tropical or South Africa, eight into some parts of tropical 
Asia, and six into arctic or temperate North America. 
Range of East Asian Birds . — To complete the evidence we 
only require to know that the East Asiatic birds are as much 
like those of Europe, as we have already shown to be the case 
when we take the point of departure from our end of the 
continent. This does not follow necessarily, because it is 
possible that a totally distinct North Asiatic fauna might there 
prevail ; and, although our birds go eastward to the remotest 
parts of Asia, their birds might not come westward to Europe. 
The birds of Eastern Siberia have been carefully studied by 
Russian naturalists and afford us the means of making the 
required comparison. There are 151 species belonging to the 
orders Passeres and Picariae (the perching and climbing birds), 
and of these no less than 77, or more than half, are absolutely 
identical with European species; 63 are peculiar to North 
Asia, but all except five or six of these are allied to European 
forms; the remaining 11 species are migrants from South- 
eastern Asia. The resemblance is therefore equally close' 
whichever extremity of the Euro-Asiatic continent we take 
as our starting point, and is equally remarkable in birds as in 
mammalia. We have now only to determine the limits of this, 
