Page - 132 - in The Origin of Species

132 ORIGIN OF SPECIES from d"; &", and f*, from having diverged at an earlier period from a^ will be in some degree distinct from the three first-named species; and lastly, o", i"" and w" will be nearly related one to the other, but, fromhavingdiverged 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 a distinct genus. The six descendants from (I) will form two sub-genera or genera. But as the original species (I) differed largely from (A), standing nearly at the extreme end of the original genus, the six descendants from (I) will, owing to inherit- ance 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 descend- ants. Hence the six new species descended from (I), and the eight descendants 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 pro- duced by descent with modification, from two or more species of the same genus. And the two or more parent-species are supposed to be 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 represents a species, the supposed progenitor of our several sub-genera and genera. It is worth while to reflect for a moment on the character of the new species f", 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. Being descended from a form which stood between the 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 two species. But as these two groups have gone on diverging in character from the type of their