Origin of Species Variorum

the extreme amount of difference in character between species a 14 and z 14 will be much greater than that between the most different of the original eleven species. The new species, moreover, will be allied to each other in a widely different mauner. Of the eight descendants from (A) the three marked a 14 , q 14 , p 14 , will be nearly related from having recently branched off from a 10 ; b 14 , and f 14 , from having diverged at an earlier period from a 5 , will be in some degree distinct from the three first-named species; and lastly, o 14 , e 14 , and m 14 , will be nearly related one to the other, but, from having diverged at the first commencement of the process of modification, will be widely different from the other five species, and may constitute a sub-genus or even a distinct genus.

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 descendants 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 intermediate 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