THE GENESIS OF SPECIES. 175 



from one point of view Mr. Darwin may be said to 

 attribute the origin of species to Variation rather 

 than Natural Selection. He is, moreover, far from 

 ignoring the influence of other principles, such as 

 Inheritance, Reversion, and Correlation, upon the 

 total result. He may be thought inconsistent with 

 himself in laying stress at times upon the minuteness 

 of the variations which he supposes to have slowly 

 accumulated into specific differences, and at other times 

 admitting the sudden appearance of variations which 

 may be considered as large ones, and which are cer- 

 tainly striking. But in the first instance the great and 

 almost overwhelming difficulty was to induce a belief 

 that forms specifically different could be connected with 

 one another by descent. By showing that a multitude 

 of small differences accumulated would make a large 

 total difference, he made as it were a bridge for the 

 existing incredulity. It now appears that the gulf 

 may be passed with easy strides instead of the little 

 slow steps at first thought necessary. This fortifies the 

 doctrine of the Transmutation of Species, in proportion 

 as there are fewer ' missing links,' fewer transitional 

 forms that need to be accounted for. 



Of ' the coexistence of closely similar structures of 

 diverse origin,' illustrated so forcibly by the instance of 

 the eye, ( in at least three independent lines of descent, 

 the Mollusca, the Annulosa, and the Vertebrata/ it can 

 scarcely be denied that Natural Selection alone would 

 be an inadequate explanation. But here again it should 

 be observed that Darwinism does not attribute every- 



