CHAPTER VII. 



THE AKGUMEXTS FROM DISTRIBUTION. 



137. IN 105 and 106, we contemplated the phenomena 

 of distribution in Space. The general conclusions reached, 

 in great part based on the evidence brought together by Mr 

 Darwin, were that, " on the one hand, we have similarly-con 

 ditioned, and sometimes nearly-adjacent, areas, occupied by 

 quite different Faunas. On the other hand, we have areas 

 remote from each other in latitude, and contrasted in soil as 

 well as climate, which are occupied by closely-allied Faunas." 

 Whence it was inferred that " as like organisms are not uni- 

 versally, or even generally, found in like habitats ; nor very 

 unlike organisms, in very unlike habitats; there is no manifest 

 pre-delermined adaptation of the organisms to the habitats." 

 In other words, the facts of distribution in Space, do not 

 conform to the hypothesis of design. At the same 



time we saw that " the similar areas peopled by dissimilar 

 forms, are those between which there are impassable barriers ; 

 while the dissimilar areas peopled by similar forms, are those 

 between which there are no such barriers ;" and these 

 generalizations appeared to be in harmony with the abund- 

 antly-illustrated truth, " that each species of organism tends 

 ever to expand its sphere of existence to intrude on other 

 areas, other modes of life, other media." 



By way of showing still more clearly the effects of this 

 competition among races of organisms, let me here add some 

 recently-published instances of the usurpations of areas, and 



