THE WHITE BLACKBERRY 337 



If this word be taken to imply that all traits 

 and tendencies of an ancestral strain are carried 

 forward from generation to generation by hered- 

 ity, even though unable to make themselves 

 manifest for many generations, and that then, 

 through some unexplained combination of tend- 

 encies, the submerged trait is enabled to come to 

 the surface and make itself manifest, the explana- 

 tion must be admitted to have a certain measure 

 of tangibility. 



Nevertheless, there is a degree of vagueness 

 about the use of the word "tendencies" that robs 

 the explanation of complete satisfactoriness. 



Meantime the human mind is always groping 

 after tangible explanations of observed phenom- 

 ena. It is always more satisfactory to be able to 

 visualize processes of nature. It was for this 

 reason that Darwin's theory that natural selec- 

 tion is the most powerful moving factor in the 

 evolution of races gained such general recogni- 

 tion and still remains as the most satisfactory of 

 all hypotheses of evolution. 



And it is for the same reason that a tangible 

 explanation of the phenomena of atavism or the 

 reversion to ancestral types has gained a tremen- 

 dous vogue in recent years. 



The explanation in question is associated with 

 the name of the Austrian monk Mendel, who 



