xxvi MUTATION, MENDELISM, ETC. 



Ethiopian Region, and, proceeding through the Oriental 

 and Australian, reach its final culmination in the astonish- 

 ingly complex associations and the wonderful resem- 

 blances, perfect in the minutest details, of the Neotropical 

 Region. 



Confidence in the theory of Gravitation is, I believe, 

 founded on indirect evidence. A continually widening 

 knowledge of the systems and movements of the Cosmos 

 remains ever consistent with the theory. The knowledge 

 itself will always be of the deepest interest, even if 

 Gravitation should ultimately be refuted or extended out 

 of recognition. So, to compare small things with great, is 

 it with the theory of Natural Selection and the evidence of 

 Mimicry. The great mimetic combinations of the various 

 degrees— grouped like planets and satellites round centres 

 of primary and secondary importance — sweep along the 

 path of Evolution, just as the gravitational systems drift 

 through space, without disturbing their internal relation- 

 ships. A rapidly-increasing knowledge of the mimetic 

 systems still remains consistent with Natural Selection, 

 and, whatever be the fate of this great theory, the facts 

 must always be interesting in a high degree. And as to 

 the ultimate fate of the theory we may use with far 

 greater confidence than in 1859 the words with which 

 Darwin sent the Origin of Species to Asa Gray :— ' I 

 cannot possibly believe that a false theory would explain 

 so many classes of facts as I think it certainly does 

 explain. On these grounds I drop my anchor, and 

 believe that the difficulties will slowly disappear.' * 



5. Mendelism and Natural Selection. 

 The relationship of Natural Selection to this recently- 

 known discovery will, I think, appear most clearly by the 

 1 Life and Letters 0/ Charles Darwin, London, 1887, vol. ii, p. 217. 



