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 varieties, and thus be
further improved through natural selection and gain further advantages.

Lastly, looking not to any one time, but at all time, if my theory be
true, numberless intermediate varieties, linking closely together all
the species of the same group, 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
among fossil remains, which are preserved, as we shall attempt to show
in a future chapter, in an extremely imperfect and intermittent record.

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

It has been asked by the opponents of such views as I hold, how, for
instance, could a land carnivorous animal 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 there now exist
carnivorous animals presenting close intermediate grades from strictly
terrestrial to aquatic habits; and as each exists by a struggle for
life, it is clear that each must be well adapted to its place in nature.
Look at the Mustela vison of North America, which has webbed feet,
and which resembles an otter in its fur, short legs, and form of tail;
during summer this animal dives for and preys on fish, but during the
long winter it leaves the frozen waters, and preys, like other polecats
on mice and land animals. If a different case had been taken, and it
had been asked how an insectivorous quadruped could possibly have been
converted into a flying bat, the question would have been far more
difficult to answer. Yet I think such difficulties have little weight.

Here, as on other occasions, I lie under a heavy disadvantage, for, out
of the many striking cases which I have collected, I can give only
one or two instances of transitional habits and structures in allied
species; and of diversified habits