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Show 38 ISLAND LIFE. [PAR'r I. We find, that out of a total of 118 British. Passeres there are: 32 species which range to North Afnca 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 Afr~ca and Western A~ia. 6 species which range to North Afnca, but not at all mto 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 temperate 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 Tequired comparison. There are 151 species belonging to the .orders Passeres and Picarire (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 Southeastern 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 ~n mammalia. We have now only to determine the limits of th1s, CllAP. Ill.] ZOOLOGICAL REGIOKS. 39 our first zooloo-ic 1 . . t' , b 0 a region, whiCh has been termed the "Palre arc .lC y Mr. Sclater, meanino- the "northern old-world,: reo-wn-a name 1 ° 0 rnl L. . now we 1 known to naturalists. .L· tLe wnts of the Palce arc tw . R egw. n.-The boundaries of this regwn, as nearly as the b . 1 Y can e ascertamed are shown on our genera map at the be · · f . ' 'd t . . gmmng o th1s chapter, but it will be evi en on considera.t wn' tha t ' except m. a few places, its limits can o· nly be approxtmately defi no· d · 0 n t h e north cast and west It extends to the ocean and includes b ' f . '1 , l · . . ' a num cr o IS ands w wse pecuhanties will be pointed out in b th h a su sequent chapter· so at t e southern boundary alone remains b,·1h · . , " t as th' ' IS runs across t e entire c?ntment from the Atlantic to tho Pacific ocean, bo ftenb l traversmg li. ttle-.k nown reo-ions we rna h o , y per aps never e a . e t_o determme It accurately, even if it admits of such determ~natwn. In drawing the boundary line across Africa we meet With our first difficulty . The Euro -A su· t tI'C am· ma1 s undoubtedly extend to the northern borders of the S h h'l h a ara, w I e t os~ of tropical Africa come up to its southern marain the desert It~elf forming a kind of dry sea between them. S~m~ of the spe~Ie~ ?n either side penetrate and even cross the deser~, but It IS Impossible to balance these with any accuracy and It. has therefore been thought best, as a mere matter of· con vemence, to consider the geographical line of the tropic of Cancer to form the boundary. We are thus enabled to define the Pal::ea:ctic. region as including all north temperate Africa; and, a Similar mtermingling of animal types occurrincr in Arabia the sam~ boundary line is continued to the south:rn shore of the Persian Gul.f. P~rsia aud Afghanistan undoubtedly belong to. the PalrearctlC regwn, and Baluchistan should probably go :vrth t.hese: The boundary in the north-western part of India IS agam drfficult to ~etermine, but it cannot be far one way or the other from the nver Indus as far up as Attock opposite the mou.th of th~ Cabool river. Here it will bend to the south-east, passmg a httle south of Cashmeer, and aloncr the southern slop~s of the Himalayas into East Thibet and China, at heights varymg from 9,000 to 11,000 feet according to soil aspect and shelter. It may, perhaps, be defined as extendin~ to th~ upper belt of forests as fa.r as coniferous trees prevail; but |