112 ON THE ORIGIN OF SPECIES 



The six descendants from (I) will form two sub- 

 genera or even genera. But as the original species (I) 

 differed largely from (A), standing nearly at the 

 extreme points of the original genus, the six de- 

 scendants 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 inter- 

 mediate species, also (and this is a very important 

 consideration), which connected the original species 

 (A) and (I), have all become, excepting (F), extinct, 

 and have left no descendants. Hence the six new 

 species descended from (I), and the eight descended 

 from (A), will have to be ranked as very distinct genera, 

 or even as distinct sub-families. 



Thus it is, as I believe, that two or more genera 

 are produced by descent with modification, from two 

 or more species of the same genus. And the two or 

 more parent -species are supposed to have descended 

 from some one species of an earlier genus. In our 

 diagram, this is indicated by the broken lines, beneath 

 the capital letters, converging in sub-branches down- 

 wards towards a single point ; this point representing a 

 single species, the supposed single parent of our several 

 new sub-genera and genera. 



It is worth while to reflect for a moment on the 

 character of the new species f 14 , which is supposed not 

 to have diverged much in character, but to have 

 retained the form of (F), either unaltered or altered 

 only in a slight degree. In this case, its affinities to 

 the other fourteen new species will be of a curious and 

 circuitous nature. Having descended from a form 

 which stood between the two parent -species (A) and 

 (I), now supposed to be extinct and unknown, it will be 

 in some degree intermediate in character between the 

 two groups descended from these species. But as these 

 two groups have gone on diverging in character from 

 the type of their parents, the new species (f 14 ) will 

 not be directly intermediate between them, but rather 

 between types of the two groups ; and every naturalist 



