CHAPTER FIFTY-FOUR 



THE BIOLOGICAL REGIONS OF THE WORLD 



1. GEOGRAPHERS divide the land regions of the world Theconti- 

 into continents : Europe, Asia, Africa, North and 

 South America, Australia. Biologists, investigating the 

 distribution of life, long ago found that these divisions spend with 

 were unnatural, in the sense that they failed to agree * 



with any definable life areas. For example, when we go 

 from western Europe to northern Japan, crossing two 

 continents, we find the plants and animals very similar 

 throughout. Very many of the species differ at the 

 extremes of this long area, but the general similarity is 

 sufficient to impress even an unscientific traveler. On 

 the other hand, if we pass from Tibet to the plains of 

 India, all in Asia, we meet with an entirely new set of 

 organisms. In America, the highlands of Mexico differ 

 extremely in their products from the lowlands along the 

 coast, the tierra calient e or hot country. 



2. In 1857 an English naturalist, P. L. Sclater, made Thebio- 

 a detailed study of the distribution of birds, and came 



to the conclusion that it was possible to define a series Sciaterand 



Wallace 



of great zoological regions, each of which would be 

 found to possess a fairly similar fauna throughout. 

 Sclater's regions were studied by A. R. Wallace, who 

 found that they were equally valid for practically all 

 groups of land animals. Later investigations showed 

 that they applied to plants also. These regions are so 

 "natural," that is to say, so recognizable by their 

 products, that any competent zoologist or botanist, 

 transported blindfolded to a point within one of them, 

 could tell which it was after half an hour's investigation. 

 Difficulty would be likely to arise only in places on or 

 near the boundary of two regions. 



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