106 RESULT OF THE ACTION 



constitution, and structure. Hence all the intermediate forms 

 between the earlier and later states, that is between the less 

 and more improved states of the same species, as well as the 

 original parent species itself, will generally tend to become 

 extinct. So it probably will be with many whole collateral 

 lines of descent, which will be conquered by later and im- 

 proved lines. If, however, the modified offspring of a species 

 get into some distinct country, or become quickly adapted to 

 some quite new station, in which offspring and 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 14 to m 14 ), and species (I) will be replaced by 

 six (n u to s 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 aiay 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 z 1 * will be 

 mucli greater than that between the most distinct of the 



