Introductory. 21 
miraculously created units of organic nature. Now, 
all that I have at present to remark is, that this 
pre-Darwinian exception which was made in favour 
of species to the otherwise recognised principle of 
gradual change, was an exception which can at no 
time have been recommended by any antecedent 
considerations. At all times it stood out of analogy 
with the principle of continuity ; and, as we shall fully 
find in subsequent chapters, it is now directly con- 
tradicted by all the facts of biological science. 
There remains one other fact of high generality to 
which prominent attention should be drawn from the 
present, or merely antecedent, point of view. On 
the theory of special creation no reason can be 
assigned why distinct specific types should present 
any correlation, either in time or in space, with their 
nearest allies; for there is evidently no conceivable 
-reason why any given species, A, should have been 
specially created on the same area and at about the 
same time as its nearest representative, B,—still less, 
of course, that such should be a general rule through- 
out all the thousands and millions of species which 
have ever inhabited the earth. But, equally of course, 
on the theory of a natural evolution this is so necessary 
a consequence, that if no correlation of such a two-fold 
kind were observable, the theory would be negatived. 
Thus the question whether there be any indication 
of such a two-fold correlation may be regarded as 
a test-question as between the two theories; for 
although the vast majority of extinct species have 
been lost to science, there are a countless number 
of existing species which furnish ample material for 
answering the question. And the answer is so un- 
