OF NA TURA L SELECTION'. 1 1 '/ 



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, four- 

 teen 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, extremely probable tliat 

 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 

 transmitted offspring to the fourteenth thousandth genera- 

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

 species (E and F) 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^* and z^^ will be much greater than that between the 

 most distinct 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", q^*, 7.?^*, will be nearly related from 

 having recently branched off from a}^; b^^ and/^*, from hav- 

 ing diverged at an earlier period from a^, will be in some 

 degree distinct from the three first-named species; and 

 lastly, o^S e" and m}^, will be nearly related one to the 

 other, but, from having diverged at the first commence- 

 ment of the process of modification, will be widely differ- 

 ent from the other five species, and may constitute a sub- 

 genus or a distinct genus. 



The six descendants from (I) will form two sub-genera 

 or genera. But as the original species (I) differed largely 

 from (A), standing nearly at the extreme end of the 

 original genus, the six descendants from (I) will, owing to 

 inheritance alone, differ considerably from the eight de- 

 scendants from (A); the two groups, moreover, are sup- 



