104 GEOGRAPHICAL DISTRIBUTION 



review. He wi4l no longer meet with species analogous to our 

 oxen, horses, bears, and large carna'ria ; large-sized quadrupeds 

 are almost entirely wanting; he will find kangaroos, flying- 

 phalangers, and the ornithoryn'chus. 



Finally, if our traveller, to get back to his own country, tra- 

 verses the vast continent of America, he will discover a fauna 

 analogous to that of the old world, but composed almost entirely 

 of different species ; he will there see monkeys with a prehensile 

 tail, large carna'ria. similar to our lions and tigers, bisons, lamas, 

 armadillos ; birds, reptiles, and insects, equally remarkable, and 

 equally new to him. 



Differences not less great in the species of animals peculiar to 

 different regions of the globe, are observed, when, instead of con- 

 fining our observations to the inhabitants of the land, we examine 

 the myriads of animated creatures that dwell in the midst of the 

 waters. Passing from the coasts of Europe to the Indian Ocean, 

 and from the latter into the American seas, we meet with fishes, 

 mollusks, crusta'ceans, and zoophytes, peculiar to each of these 

 regjons. This limitation or colonization of species, whether 

 aquatic or terrestrial, is so marked, that a slightly experienced 

 naturalist cannot mistake, even at first sight, the original localities 

 of zoological collections that may have been gathered in one or 

 the other of the great geographical divisions of the globe, and 

 submitted to his examination. The fauna of each of these divi- 

 sions is peculiar to it, and may be easily characterized by the 

 presence of certain more or less remarkable species. 



Naturalists have formed many theories to account for this mode 

 of distribution of animals over the surface of the globe ; but, in 

 the present state of science, it is impossible to give a satisfactory 

 explanation, without admitting that, in the beginning, the different 

 species had their origin in the different regions where they are 

 found, and that by degrees they afterwards spread afar and occu- 

 pied a more or less considerable portion of the surface of the 

 earth. In short, the presence of a particular animal within nar- 

 row limits on the earth, necessarily supposes, when this animal 

 is found nowhere else, that it had its origin on this spot, or that 

 it imigrated there from a more or less remote region, and that 

 subsequently it was entirely destroyed where its race commenced, 

 that is, exactly at the place where, according to every probability, 

 all circumstances most favourable to its existence were found in 

 combination. There is nothing strongly in favour of this last 

 hypothesis, and it is repugnant to common sense to believe that, 

 in the beginning, the same country saw the birth of the horse, 

 the giraffe, bison, and kangaroo, for instance, but that these ani- 

 mals left it afterwards, without leaving any trace of their pas- 

 sage, to colonize, one on the steppes of central Asia, another in 



