EVOLUTION BY CHOICE 



4G3 



some salt in them already, and this might favor the seedlings 

 enduring a larger amount of salt as they grew. Sooner or 

 later the constitutional equilibrium of the plants would be 

 so disturbed that a mutation would result. Several successive 

 mutations might occur as seeds fell into Salter and Salter 

 localities. At last would appear a form like our seaside 

 crovrfoot (Fig. 303) able to thrive where the salt is strong 

 and showing many marks of its effect. The first mutation 

 would give an hereditary salt-preferring type, while a succes- 



FiG. .303. — Seaside Crowfoot {Ranunculus Cymhalaria, Crowfoot Family, 

 Ranunculaceoe). (Britton and Brown.) — Perennial herb 4-22 cm. tall; 

 leaves fleshy, smooth throughout; flowers yellow; fruit dry. Native 

 home, Northern North America and Eurasia. 



sion of mutations caused by similar responses would produce 

 a distinct species. 



The case of our stranded buttercups might be paralleled 

 by an animal which in time of famine, was reduced to the 

 choice of eating or rejecting unaccustomed food, and as a 

 result of eating enough of it to sustain hfe, being modified 

 in its habits and structure to the point of producing muta- 

 tions. Whatever share in the final result of such an evolu- 

 tionary process we may attribute to acciuirement or to selec- 

 tion we are still free to believe that it is the choice of 



