96 THE ORIGIN OF SPECIES 



stitution, and structure. Hence all the intermediate forms between 

 the earlier and later states, that is between the less and more im- 

 proved 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 improved 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 considerable 

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

 will have become extinct, being replaced by eight new species (a 14 

 to w 14 ), and species (I) will be replaced by six (» 14 to z 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 seme 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 like- 

 wise 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 diver- 

 gent tendency of natural selection, the extreme amount of differ- 

 ence in character between species a 14 and z 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 



