122 NATURAL SELECTION. Chap. IV. 



modified offspring of a species get into some distinct 

 country, or become quickly adapted to some quite new 

 station, in which child and parent do not come into 

 competition, both may continue to exist. 



If then our diagram be assumed to represent a 

 considerable amount of modification, species (A) and 

 all the earlier varieties will have become extinct, 

 having been replaced by eight new species (a 14 to m l4 ) ; 

 and (I) will have been replaced by six (n u to z u ) new 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 dif- 

 fused 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 transmitted offspring to the 

 fourteen-thousandth generation. 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. 



