GEOGRAPHICAL DISTRIBUTION. in 



Direct Creation, for the whole system of 

 Nature would then become either an unintel- 

 ligible enigma, or an arrangement expressly 

 contrived to mislead all who seek to inquire 

 into its origin.* 



The problems of Geographical Distribution 

 are certainly not without their difficulties, even 

 on the theory of Evolution, but we may expect 

 that these will be lessened in proportion to the 

 gradual increase of our knowledge. It appears 

 that when dominant species have become deve- 

 loped in a particular district, they spread from 

 it, as from a common centre, as far as they can 

 do so unchecked, and branch out ultimately 

 into different varieties. 



If a large area favourable for their exten- 

 sion exists, without geographical barriers, they 

 may remain unchanged throughout their entire 

 range, but if a colony should happen to 

 become isolated from the original stock, and 

 shut up in a limited district with different or 

 fewer competitors, it will be more liable to 

 become modified into a new form. 



*The last proposition is ludicrously illustrated by an old theory that 

 fossils were objects brought by the devil from the moon, to deceive 

 geologists as to the age of the earth. 



