EFFECTS OF NATURAL SELECTION 131 



progenitor do not come into competition, both may continue 

 to exist. 



If, then, our diagram be assumed to represent a consider- 

 able amount of modification, species (A) and all the earlier 

 varieties will have become extinct, being replaced by eight 

 new species (a" to m") ; and species (I) will be replaced by 

 six (n" to 2") 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 dififused 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 amoimt 

 of difference in character between species o" and ^r" 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 fl", 7", />'*, 

 will be nearly related from having recently branched off 



