110 TIIK GENESIS OF SPECIES. [Chap. 



space — in other words, the geograj)hicjil distribution of 

 organisms — it will be necessar}'^ to return somewhat to the 

 subject of the independent origin of ch^sely-similar forms, 

 in reirard to which some additional remarks will be found 

 toward the end of the seventh chapter. 



In this third chapter an effort has been made to show 

 that while on the Darwinian theory concordant variations 

 are extremelj'^ improbable, yet Nature ])resents us with 

 abundant examj)les of such ; the most striking of which 

 are, jierhaps, the higher organs of sense. Also that an im- 

 portant influence is exercised by conditions connected with 

 geographical distribution, but that a deeper-seated influence 

 is at work, which is hinted at by those special tendencies 

 in definite directions, which are the properties of certain 

 groups. Finally, that these facts, when taken together, 

 afford strong evidence that "Natural Selection" has not 

 been the exclusive or predominant cause of the various or- 

 ganic structural peculiarities. This conclusion has also 

 been reiinforced by the consideration of jjlienomena pre- 

 sented to us b}' the inorganic world. 



