tive
species. In this case, intermediate varieties between the several
representative species and their common parent, must formerly have
existed in each broken portion of the land, but these links will
have been supplanted and exterminated during the process of natural
selection, so that they will no longer exist in a living state.

Thirdly, when two or more varieties have been formed in different
portions of a strictly continuous area, intermediate varieties will, it
is probable, at first have been formed in the intermediate zones, but
they will generally have had a short duration. For these intermediate
varieties will, from reasons already assigned (namely from what we know
of the actual distribution of closely allied or representative species,
and likewise of acknowledged varieties), exist in the intermediate zones
in lesser numbers than the varieties which they tend to connect. From
this cause alone the intermediate varieties will be liable to accidental
extermination; and during the process of further modification through
natural selection, they will almost certainly be beaten and supplanted
by the forms which they connect; for these from existing in greater
numbers will, in the aggregate, present more variation, and thus be
further improved through natural selection and gain further advantages.

Lastly, looking not to any one time, but to all time, if my theory be
true, numberless intermediate varieties, linking most closely all the
species of the same group together, must assuredly have existed; but the
very process of natural selection constantly tends, as has been so often
remarked, to exterminate the parent forms and the intermediate links.
Consequently evidence of their former existence could be found only
amongst fossil remains, which are preserved, as we shall in a future
chapter attempt to show, in an extremely imperfect and intermittent
record.

ON THE ORIGIN AND TRANSITIONS OF ORGANIC BEINGS WITH PECULIAR HABITS AND
STRUCTURE.

It has been asked by the opponents of such views as I hold, how, for
instance, a land carnivorous animal could have been converted into one
with aquatic habits; for how could the animal in its transitional state
have subsisted? It would be easy to show that within the same group
carnivorous animals exist having every intermediate grade between
truly aquatic and strictly terrestrial habits; and as each exists by a
struggle for life, it is clear that each is well adapted in its