[10 THE GENESIS OF SPECIES. [CHAP. 



space in other words, the geographical distribution of 

 organisms it will be necessary to return somewhat to the 

 subject of the independent origin of closely-similar forms, 

 in regard 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 extremely improbable, yet Nature presents us with 

 abundant examples of such ; the most striking of which 

 are, perhaps, 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 reenforced by the consideration of phenomena pre- 

 sented to us by the inorganic world. 



