NATURAL SELECTION 111 



and D, than to the other species ; and species (I) more 

 to G, H, K, L, than to the others. These two species 

 (A) and (I), were also supposed to be very common and 

 widely diffused species, so that they must originally 

 have had some advantage over most of the other species 

 of the genus. Their modified descendants, fourteen in 

 number at the fourteen -thousandth generation, will 

 probably have inherited some of the same advantages : 

 they have also been modified and improved in a 

 diversified manner at each stage of descent, so as to 

 have become adapted to many related places in the 

 natural economy of their country. It seems, therefore, 

 to me extremely probable that they will have taken 

 the places of, and thus exterminated, not only their 

 parents (A) and (I), but likewise some of the original 

 species which were most nearly related to their parents. 

 Hence very few of the original species will have trans- 

 mitted offspring to the fourteen -thousandth genera- 

 tion. We may suppose that only one (F), of the two 

 species which were least closely related to the other 

 nine original species, has transmitted descendants to 

 this late stage of descent. 



The new species in our diagram descended from the 

 original eleven species, will now be fifteen in number. 

 Owing to the divergent tendency of natural selection, 

 the extreme amount of difference in character between 

 species a 14 and z 14 will be much greater than that 

 between the most different of the original eleven 

 species. The new species, moreover, will be allied 

 to each other in a widely different manner. Of the 

 eight descendants from (A) the three marked a 14 , q u , 

 p H , will be nearly related from having recently 

 branched off from a 10 ; b u and/ 14 , from having diverged 

 at an earlier period from a 6 , will be in some degree dis- 

 tinct from the three first-named species ; and lastly, 

 o 14 , e u , and m 14 , will be nearly related one to the other, 

 but from having diverged at the first commencement of 

 the process of modification, will be widely different from 

 the other five species, and may constitute a sub-genua 

 or even a distinct genus. 



