IN THE LAST HALF- CENTURY. 95 



influence of conditions, which no one 

 could deny to be a matter of fact, when 

 his attention was drawn to the evidence ; 

 and ^;he occurrence of great geological 

 changes which also was matter of fact ; 

 could be used as the only necessary pos- 

 tulates of a theory of the evolution of 

 plants and animals which, even if not, at 

 once, competent to explain all the known 

 facts of biological science, could not be 

 shown to be inconsistent with any. So 

 far as biology is concerned, the publica- 

 tion of the 'Origin of Species,' for the 

 first time, put the doctrine of evolution, 

 in its application to living things, upon a 

 sound scientific foundation. It became 

 an instrument of investigation, and in no 

 hands did it prove more brilliantly profit- 

 able than in those of Darwin himself. 

 His publications on the effects of domesti- 

 cation in plants and animals, on the influ- 

 ence of cross-fertilisation, on flowers as 

 organs for effecting such fertilisation, on 



