Page - 142 - in The Origin of Species

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