Chap. I. STRUCTURE AND GEOGRAPHICAL DISTRIBUTION. 37 



tioii with the study of the influence of physical agents upon the character of animals 

 and plants in diflerent parts of the world. North America certainly does not resem- 

 l)le Europe and Northern Asia, more than parts of Australia resemble certain parts 

 of Africa or of Soutli America, and even if a greater diflerence shoidd be conceded 

 between the latter than between the former, these disparities are in no way com- 

 mensurate with the difference or similarity of their organized beings, nor in any way 

 rationally dependent one upon the other. Why should the identity of species pre- 

 vailing in the Arctics not extend to the temperate zone, when many species of this 

 zone, though difterent, are as difficult to distinguish, as it is difficult to prove the 

 identity of certain arctic species, in the diffijrent continents converging to the north, 

 and when besides, those of the two zones mingle to a great extent at their boun- 

 daries? Why are the antarctic species not identical with those of the arctic regions? 

 And Avhy should a further increase of the average temperature introduce such com- 

 pletely new types, when even in the Arctics, there are in different continents such 

 strikingly peculiar types (the Ehytina for instance,) combined with those that are 

 identical over the whole arctic area?^ 



It may at first sight seem very natural that the arctic species should extend 

 over the three northern continents converging towards the north pole, as there can 

 be no insuperable barrier to the widest dissemination over this whole area for ani- 

 mals living in a glacial ocean or upon parts of three continents which are almost 

 bound together by ice. Yet the more we trace tliis identity in detail, the more 

 surprising does it appear, as we find in the Arctics as weU as everj^vhere else, repre- 

 sentatives of different types living together. The arctic Mammalia belonging chiefly 

 to the fixmilies of Whales, Seals, Bears, Weasels, Foxes, Ruminants and Rodents, 

 have, as Mammalia, the same general structure as the Mammalia of any other part 

 of the globe, and so have the arctic Birds, the arctic Fishes, the arctic Articulata, the 

 arctic MoUusks, the arctic Radiata when compared to the representatives of the same 

 types all over our globe. This identity extends to every degree of affinity among 

 these animals and the plants which accompany them ; their orders, their families, and 

 their genera as far as they have representatives elsewhere, bear everpvhere the 

 same identical ordinal, family, or generic characters; the arctic foxes have the same 



' I beg not to be misunderstood. I do not im- point under eonsideration. Too little attention has 



pute to all naturalists the idea of aseribing all the thus far been paid to tlie faets bearing upon the 



differences or all the similarities of the organic peculiarities of structure of animals in connection 



world to climatic influences; I wisli only to ri'iuiiid willi the ran;:e of their distribution. Sui'li investi- 



them that even the truest picture of the correla- gations are only beginning to be made, as native 



tions of climate and geographical distribution, does investigators are studying comparatively the anatomy 



not yet touch the question of origin, which is the of animals of diflerent continents. 



