ive group of diverging
dotted lines to be very great, the forms marked a14 to p14, those marked
b14 and f14, and those marked o14 to m14, will form three very distinct
genera. We shall also have two very distinct genera descended from
(I) and as these latter two genera, both from continued divergence of
character and from inheritance from a different parent, will differ
widely from the three genera descended from (A), the two little groups
of genera will form two distinct families, or even orders, according to
the amount of divergent modification supposed to be represented in the
diagram. And the two new families, or orders, will have descended from
two species of the original genus; and these two species are supposed
to have descended from one species of a still more ancient and unknown
genus.

We have seen that in each country it is the species of the larger genera
which oftenest present varieties or incipient species. This, indeed,
might have been expected; for as natural selection acts through one form
having some advantage over other forms in the struggle for existence,
it will chiefly act on those which already have some advantage; and
the largeness of any group shows that its species have inherited from
a common ancestor some advantage in common. Hence, the struggle for the
production of new and modified descendants, will mainly lie between the
larger groups, which are all trying to increase in number. One large
group will slowly conquer another large group, reduce its numbers, and
thus lessen its chance of further variation and improvement. Within the
same large group, the later and more highly perfected sub-groups, from
branching out and seizing on many new places in the polity of Nature,
will constantly tend to supplant and destroy the earlier and less
improved sub-groups. Small and broken groups and sub-groups will finally
tend to disappear. Looking to the future, we can predict that the groups
of organic beings which are now large and triumphant, and which are
least broken up, that is, which as yet have suffered least extinction,
will for a long period continue to increase. But which groups will
ultimately prevail, no man can predict; for we well know that many
groups, formerly most extensively developed, have now become extinct.
Looking still more remotely to the future, we may predict that, owing to
the continued and steady increase of the larger groups, a multitude
of smaller groups will become utterly ex