88 KESULTS OF THE ACTION OP [CHAP. IV. 



will have become extinct, being replaced by eight new species 

 (a u to t") ; and species (I) will be replaced by six (n u to 2 14 ) new 

 species. 



But we may go further than this. The original species of our 

 genus were supposed to resemble each other in unequal degrees, 

 as is so generally the case in nature; species (A) being more 

 nearly related to B, C, 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, 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 transmitted offspring to the 

 fourteen-thousandth generation. We 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 14 and 2 14 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 14 , q u , /> 14 , will be nearly related from having 

 recently branched off from a 10 ; b l \ and / u , from having diverged 

 at an earlier period from a 5 , will be in some degree distinct from 

 the three first-named species ; and lastly, o 14 , c 14 , and m l \ 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- 

 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 descendants from (A); the two groups, moreover, are 

 supposed to have gone on diverging in different directions. The 



