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and beneficial (lualitics liapix'ii to arise as sli.i::lit varia- 

 tions from the ancestral tyi)e, they will (other t]iiii.i::s 

 permittini*')? l^e seized upon by natural selection, and 

 being transmitted by heredity to subsequent lynerations, 

 will be added to the })reviously existinjy;- type.^Tliis then, 

 is natural selection or the survival of the fittest, ''the 

 one term referring- mainly to the ]n'ocoss, tlie other to 

 the result/^ 



The process is analogous to that by wliich the gardener 

 and the catth'-breeder bring about tlicir wonderful re- 

 sults. Just as these men, by always "selecting" tlicii- 

 l)est individuals to breed from, slowly but continuously 

 improve their stock, so Nature by a process of "selec- 

 tion," slowly but continuously makes the various species 

 of plants and animals better suited to the conditions of 

 their life. What the skill of Luther Burbank has ac- 

 complished in the course of a few generations. Nature 

 takes years or even centuries of experimental ion to pro- 

 duce i>y artificial selection, man woi-ks on external 

 characters irregularly ami imperfectly for a short time. 

 Nature works on the whole machinery of life by con- 

 sistent accumulation during whole geological epochs. 

 Silently and insensibly working, natural selection is daily 

 and liourh^ scrutinizing the slightest variations, "reject- 

 ing those that are bad, preserving and adding up all that 

 are good." '^ 



Tender natural conditions there is an endless range of 

 variation. We have seen in chapter I, how like tends 

 to beget like, but that although the offspring is similar to 

 the parent there is never precise redu]')lication. There 

 is latitude allowed for individual variation. The indi- 

 vidual differences are due to age, sex, modification, and 



•*> 'riioiiison & ricMulos. o/». cit.. ]>. l.Td. 



