446 KINSHIP AND ADAPTATION 



indistinguishable from wild plants of the same species. But 

 might not very long subjection to changed conditions finally 

 fix an acquired character? Possibly, and it should be said 

 that the botanical evidence is perhaps more favorable to this 

 view than the zoological; but if the facts can be explained 

 without relying upon suppositions hardlj' possible to verify, 

 we may build upon a safer foundation. 



167. Selected adaptations. Dissatisfaction witli La- 

 marck's explanation of modification through acquirement, 

 deterred most of his contemporaries from accepting the theory 

 of evolution, and it was not until Charles Darwin and Alfred 

 Russel Wallace offered an explanation based ujjon acknowl- 

 edged facts that evolutionism was welcomed at all widely 

 by scientific thinkers. The new doctrine is generallj' known 

 as Darwinism, because Darwin's contributions in support of 

 it were most extensive and important, although both Darwin 

 and Wallace, working ([uite independently, came to sub- 

 stantially the same conclusions, and announced them at the 

 same meeting of the Linneean Society of London in 1858. 



Darwin felt that the problem of how one species changes 

 into another might best be attacked by studying the modi- 

 fications which plants and animals undergo when domesti- 

 cated. We have already seen (page 12(3) how much has been 

 accomplished with cultivated plants by artificial selection, — 

 farmers taking their seed from those individuals which please 

 them best antl continuing to pick out for propagation year 

 after year the plants which show most fully those most de- 

 sirable features. Here it W(jul(l seem as if hereditary pecul- 

 iarities were surely depended upon, and that the most strik- 

 ing departures from an original f(jrm represented the sum of 

 many small differences in one chrection accumulated through 

 successive generations by inheritance. Darwin reasoned 

 that if it could be shown that plants and animals in nature 

 were continually suljjected to agencies which favored the 

 propagation of individuals possessed of slight hereditary- 

 peculiarities contrif)uting to their welfare, the most perfect 

 adaptations would be accomited I'or and the origin of species 

 scientifically explained. 



What natural agencies can be supposed to exert a selective 



