TO THE LOWER ANIMALS. 127 



If it is inconsistent with any one phenomenon, it must be 

 rejected ; if it fails to explain any one phenomenon, it is 

 so far weak, so far to be suspected ; though it may have a 

 perfect right to claim provisional acceptance. 



Now, Mr. Darwin's hypothesis is not, so far as I am 

 aware, inconsistent with any known biological fact ; on 

 the contrary, if admitted, the facts of Development, of 

 Comparative Anatomy, of Geographical Distribution, and 

 of Palaeontology, become connected together, and exhibit 

 a meaning such as they never possessed before ; and I, for 

 one, am fully convinced that if not precisely true, that hy- 

 pothesis is as near an approximation to the truth as, for 

 example, the Copernican hypothesis was to the true theory 

 of the planetary motions. 



But, for all this, our acceptance of the Darwinian hy- 

 pothesis must be provisional so long as one link in the 

 chain of evidence is wanting ; and so long as all the ani- 

 mals and plants certainly produced by selective breeding 

 from a common stock are fertile, and their progeny are 

 fertile with one another, that link will be wanting. For, 

 so long, selective breeding will not be proved to be com- 

 petent to do all that is required of it to produce natural 

 species. 



I have put this conclusion as strongly as possible be- 

 fore the reader, because the last position in which I wish 

 to find myself is that of an advocate for Mr. Darwin's, or 

 any other views if by an advocate is meant one whose 

 business it is to smooth over real difficulties, and to per- 

 suade where he cannot convince. 



In justice to Mr. Darwin, however, it must be admitted 

 that the conditions of fertility and sterility are very ill 

 understood, and that every day's advance in knowledge 

 leads us to regard the hiatus in his evidence as of less and 

 less importance, when set against the multitude of facts 



