48G ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



the areas they inhabited. This has apparently progressed to 

 such an extent that various types have been able to accom- 

 modate themselves to, or have been modified for, the various 

 climates, and thus, to a large extent, isothermal distribution 

 has been subordinated to land distribution. 



As to the (1) Arctic and (2) North Temperate realms, we 

 may well hesitate to admit that there is any such distinction 

 between them as to compel us to contradistinguish the latter, 

 as a whole, against the former. Indeed, the former seems to 

 be almost only definable by negative characters, and to be 

 now neutral ground, from which, by the rigor of the climate, 

 most forms of animal life have been excluded ; while the " re- 

 gions" of the latter have each their own peculiarities, which 

 entitle them to recognition as independent "realms" far 

 more than do the characteristics of the Arctic a like rank. 



With respect to the (3) Indo-European realm, another set 

 of considerations come up for notice. Mr. Allen distributes 

 the 49 families of mammals represented in the "realm" un- 

 der four categories: (1) "12 common to both regions, and 

 also of wide extralimital range;" (2) "18 common to both 

 regions;" (3) "10 peculiar to the African region;" and (4) 

 " 9 occurring in the Indian region, but not in the African." 

 Mr. Allen has evidently been especially influenced by the 

 figures of the second category, but has apparently not consid- 

 ered one circumstance of vital importance. While it is quite 

 true that most of the 18 families enumerated are now in great 

 part confined to the two " regions " in question, in the Terti- 

 ary epoch almost all ranged far to the northward in Europe, 

 and several into America, and the present restriction is due 

 partly to the change of climate and partly to the encroach- 

 ments of the human race. Indeed, the first and second 

 categories may well be combined in this consideration ; and 

 then the distinctive peculiarities of the Indian and African 

 regions will be seen to be quite decided. These distinctive 

 peculiarities are reinforced to such an extent by the pecu- 

 liarities of other classes especially the fishes that instead 

 of combining the two, we should rather be disposed to con- 

 trast the African against the Indian in connection with the 

 " Europreo-Asiatic region." 



Passing over other open questions, it need only be added 

 that there are almost as good, if not even better, reasons for 



