228 AFFINITIES AND GEOGRAPHICAL 



thus, for example, have one flora surrounding the Medi- 

 terranean, which is the fact. So it is also likely that islands 

 should botanically and zoologically partake of the character of 

 the neighbouring continents. In regions, on the other hand, 

 sufficiently distant to be involved in the influence of diverse 

 foci of life, we are to expect differences proportioned .to the 

 difference of original elements, and also of conditions attending 

 the development of the various lines : there we may only ex- 

 pect to see such ultimate parities attained as those between the 

 emeu of Australia and the rhea of America, or the jaguar and 

 puma of the latter continent and the tiger of Asia. Here it 

 is important to observe that the cetacea and the marine birds 

 in the neighbourhood of the different continents, present less 

 variation than do the land mammals and birds : they have 

 advanced less way along the lines, and have been less exposed 

 to the conditions productive of external variations. In the 

 case of a well-defined zoological region, such as the northern 

 parts of North America, we see the indigenous animals ex- 

 pressly confined to those families which our plan sets forth as 

 springing from the marine tribes above adverted to. There is 

 the polar bear, with his various progeny, the brown bear, black 

 bear, the wolf, fox, and dog ; these from a phocal ancestry. 

 The sea-otter, sprung from an allied stodfe, gives birth to the 

 few musteline animals which dwell in these dreary regions. 

 Then we have herbivorous cetes, giving rise to the moose deer 

 and musk ox, these again being the progenitors of the goat and 

 sheep. And, finally, we have the unusually numerous rodents 

 from the aquatic birds, which nowhere are seen in greater 

 numbers than on the borders of the Arctic Ocean. Such, 

 with the mole, is the whole show of mammalia in this pro- 

 vince : it is, it will be observed, of a limited kind ; but it is 

 interesting to remark that it presents nearly all the animals of 

 that class, which we have supposed, from their affinities, to be 

 descended from the marine families of which there is such 

 abundance upon the adjacent ocean. And, supposing this 

 ocean to be the berceau of these land animals, we can easily 

 see why they should be more akin to the terrestrial mammalia 

 of Northern Burope than to those of South America. The 

 Northern Ocean, spreading in one character of climate along 

 the confines of the two first regions, enables a set of maritime 

 animals which may have come into existence in any part of it, 

 to spread into the two continents alike the same bear, nearly 

 the same ruminants, and so forth ; but, if the Southern Ocean 



