52 EVOLUTION OF TO-DAY. 



When challenged to produce a new species by varia- 

 tion they acknowledge their inability to do so, and 

 demand more time. Direct evidence is therefore 

 not sufficient either to prove or disprove the muta- 

 bility of species. Meantime the scientist claims that 

 he can bring forward enough indirect evidence to 

 substantiate the theory of evolution ; since all of the 

 facts of the organic world appear to him to be in 

 conformity with the belief that species have been 

 evolved. To this indirect evidence we will devote 

 the next four chapters. 



