142 ORIGIN OF SPECIES 



characters useful to the males alone, in their struggles or 

 rivalry with other males ; and these characters will be trans- 

 mitted to one sex or to both sexes, according to the form of 

 inheritance which prevails. 



Whether natural selection has really thus acted in adapting 

 the various forms of life to their several conditions and sta- 

 tions, must be judged by the general tenor and balance of 

 evidence given in the following chapters. But we have al- 

 ready seen how it entails extinction; and how largely ex- 

 tinction has acted in the world's history, geology plainly 

 declares. Natural selection, also, leads to divergence of 

 character; for the more organic beings diverge in structure, 

 habits, and constitution, by so much the more can a large 

 number be supported on the area, — of which we see proof by 

 looking to the inhabitants of any small spot, and to the pro- 

 ductions naturalised in foreign lands. Therefore, during the 

 modification of the descendants of any one species, and dur- 

 ing the incessant struggle of all species to increase in num- 

 bers, the more diversified the descendants become, the better 

 will be their chance of success in the battle for life. Thus 

 the small differences distinguishing varieties of the same spe- 

 cies, steadily tend to increase, till they equal the greater dif- 

 ference? between species of the same genus, or even of 

 distinct genera. 



We have seen that it is the common, the wndely-diffused 

 and widely-ranging species, belonging to the larger genera 

 within each class, which vary most; and these tend to trans- 

 mit to their modified offspring that superiority which now 

 makes them dominant in their own countries. Natural selec- 

 tion, as has just been remarked, leads to divergence of 

 character and to much extinction of the less improved and 

 intermediate forms of life. On these principles, the nature 

 of the afl^nities, and the generally well-defined distinctions 

 between the innumerable organic beings in each class 

 throughout the world, may be explained. It is a truly won- 

 derful fact — the wonder of which we are apt to overlook 

 from familiarity — that all animals and all plants through- 

 out all time and space should be related to each other in 

 groups, subordinate to groups, in the manner which we 

 everywhere behold — namely, varieties of the same species 



