380 
DARWINISM 
CHAP. 
whelming idea does this give us of the destruction of whole 
piles of rock, miles in thickness and covering areas comparable 
with those of continents; and how great must have been the 
loss of the innumerable fossil forms which those rocks con¬ 
tained ! In view of such destruction we are forced to conclude 
that our palaeontological collections, rich though they may 
appear, are really but small and random samples, giving no 
adequate idea of the mighty series of organism which have 
lived upon the earth. 1 
Admitting, however, the extreme imperfection of the geo¬ 
logical record as a whole, it may be urged that certain limited 
portions of it are fairly complete—as, for example, the various 
Miocene deposits of India, Europe, and North America,— 
and that in these we ought to find many examples of species 
and genera linked together by intermediate forms. It may be 
replied that in several cases this really occurs ; and the reason 
why it does not occur more often is, that the theory of 
evolution requires that distinct genera should be linked 
together, not by a direct passage, but by the descent of both 
from a common ancestor, which may have lived in some much 
earlier age the record of which is either wanting or very in¬ 
complete. An illustration given by Mr. Darwin will make this 
more clear to those who have not studied the subject. The 
fantail and pouter pigeons are two very distinct and unlike 
breeds, which we yet know to have been both derived from the 
common wild rock-pigeon. Now, if we had every variety of 
living pigeon .before us, or even all those which have lived 
during the present century, we should find no intermediate 
types between these two — none combining in any degree the 
characters of the pouter with that of the fantail. Neither 
should we ever find such an intermediate form, even had there 
been preserved a specimen of every breed of pigeon since 
the ancestral rock - pigeon was first tamed by man — a 
period of probably several thousand years. We thus see 
that a complete passage from one very distinct species to 
another could not be expected even had we a complete record 
of the life of any one period. What we require is a complete 
1 The reader wlio desires to understand this subject more fully, should 
study chap. x. of the Origin of Species, and chap. xiv. of Sir Charles Lyell's 
Principles of Geology. 
