LECTURE XXVIII 



ARTIFICIAL AND NATURAL SELECTION 



The comparison of artificial and natural se- 

 lection has furnished material support for the 

 theory of descent, and in turn been the object 

 of constant criticism since the time of Darwin. 

 The criticisms, in greater part, have arisen 

 chiefly from an imperfect knowledge of both 

 processes. By the aid of distinctions recently 

 made possible, the contrast between elementary 

 species and improved races has become much 

 more vivid, and promises to yield better results 

 on which to base comparisons of artificial and 

 natural selection. 



Elementary species, as we have seen in 

 earlier lectures, occur in wild and in culti- 

 vated plants. In older genera and systematic 

 species they are often present in small numbers 

 only, but many of the more recent wild types 

 and also many of the cultivated forms 

 are very rich in this respect. In agriculture 

 the choice of the most adequate elementary 

 forms for any special purpose is ac- 



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