42 FIFTY YEARS OF DARWINISM 



adaptation in response to a definite stimulus. To 

 stereotype the result would be to convert a benefit 

 to the individual into an injury to the species. 

 The beech in a very shady place would presum- 

 ably develop the maximum of the shade foliage. 

 How disadvantageous would the hereditary bias 

 be to its offspring that happened to grow in more 

 exposed situations. But, it is argued, in plants 

 subject to a permanent condition we do meet 

 with a permanent structure, just as if repetition 

 had at length produced a hereditary result. The 

 answer to this argument seems to me to be 

 complete. When conditions are uniform and 

 no power of individual adaptation is required, 

 Natural Selection, without attaining the power, 

 would produce the permanent and hereditary 

 result in the usual way. If, however, a species, 

 already possessing the power, ultimately came 

 to live permanently in one set of conditions and 

 thus ceased to need it, the power itself, no longer 

 sustained by selection, would sooner or later be 

 lost. 



DARWIN'S VIEWS ON EVOLUTION BY 

 'MUTATION' 



It is interesting to note that the word ' Muta- 

 tion ' appears at one time to have suggested itself 

 to Darwin l in order to express the evolution or 



This seems clear from the following passage in a letter 

 written Feb. 14 [1845], to Rev. L. Blomefield (Jenyns) : ' Thanks 

 for your hint about terms of " mutation ", etc. ; I had some 

 suspicions that it was not quite correct, and yet 1 do not yet see 



