Chap. VI. 
TRANSITIONAL HABITS. 
179 
tend to connect. From this cause alone the interme¬ 
diate varieties will be liable to accidental extermination ; 
and during the process of further modification througli 
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 habits 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 
