We may suppose that only one (F), of
the two species 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 a14 and z14 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
manner. Of the eight descendants from (A) the three marked a14, q14,
p14, will be nearly related from having recently branched off from
a10; b14 and f14, from having diverged at an earlier period from a5,
will be in some degree distinct from the three first-named species;
and lastly, o14, e14, and m14, 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, differ considerably
from the eight descendants from (A); the two groups, moreover, are
supposed to have gone on diverging in different directions.
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