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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
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,
for a long
continue to increase. But which groups will ultimately prevail, no man can predict; for we
know that many groups, formerly most extensively developed, have now become extinct. Looking still more remotely to the future, we may predict
owing to the continued and steady increase of the larger groups, a multitude of smaller groups will become utterly extinct, and leave no modified descendants; and consequently
of the species living at any one period, extremely few will transmit descendants to a remote futurity. I shall have to return to this subject in the chapter on Classification, but I may add that
→on
this
extremely few of the more ancient species
transmitted
→and on the view of
all the descendants of the same species
a class, we can understand how it is that there
few classes in each main division of the animal and vegetable kingdoms. Although
few of the most ancient species
→now have living and
modified descendants,
at
remote geological
the earth may have been
well peopled with
species of many genera, families, orders, and classes, as at the present
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