Chap. XI. GEOGRAPHICAL DISTRIBUTION. 349 



and the eastern shores of Africa, on almost exactly 

 opposite meridians of longitude. 



A third great fact, partly included in the foregoing 

 statements, is the affinity of the productions of the 

 same continent or sea, though the species themselves 

 are distinct at different points and stations. It is 

 a law of the widest generality, and every continent 

 offers innumerable instances. Nevertheless the natu- 

 ralist in travelling, for instance, from north to south 

 never fails to be struck by the manner in which suc- 

 cessive groups of beings, specifically distinct, yet clearly 

 related, replace each other. He hears from closely 

 allied, yet distinct kinds of birds, notes nearly similar, 

 and sees their nests similarly constructed, but not quite 

 alike, with eggs coloured in nearly the same manner. 

 The plains near the Straits of Magellan are inhabited 

 by one species of Khea (American ostrich), and north- 

 ward the plains of La Plata by another species of the 

 same genus ; and not by a true ostrich or emeu, like 

 those found in Africa and Australia under the same 

 latitude. On these same plains of La Plata, we see 

 the agouti and bizcacha, animals having nearly the 

 same habits as our hares and rabbits and belonging to 

 the same order of Kodents, but they plainly display 

 an American type of structure. We ascend the lofty 

 peaks of the Cordillera and we find an alpine species 

 of bizcacha ; we look to the waters, and we do not find 

 the beaver or musk-rat, but the coypu and capybara, 

 rodents of the American type. Innumerable other in- 

 stances could be given. If we look to the islands off 

 the American shore, however much they may differ in 

 geological structure, the inhabitants, though they may 

 be all peculiar species, are essentially American. AW 

 may look back to past ages, as shown in the last 

 chapter, and we find American types then prevalent on 



