LUTHER BURBANK 



Even the bacterium changes its constitution 

 somewhat in response to the conditions of temper- 

 ature and nutriment in which it finds itself. By 

 altering the medium and thus the food in which 

 bacteria grow, it has been found possible to 

 change their constitution so markedly that viru- 

 lent types become relatively innocuous in the 

 course of a few generations. Recent experiments 

 suggest that the same thing may be accomplished 

 by treating bacteria with ultra-violet rays, not 

 sufficiently intense to destroy their vitality. 



In a word, very marked modifications in the 

 constitution of the single-celled organism may be 

 produced by altered conditions of its tangible 

 environment. 



And these modifications are, as a matter of 

 course, passed on to the descendants of the bac- 

 terium, inasmuch as these descendants constitute, 

 essentially, portions of the parent form. 



Exactly the same thing applies to the allied 

 process of reproduction of the germ-plasm cells of 

 the higher organism. Modified conditions of en- 

 vironment changed conditions of temperature 

 and of nutrition may in some cases modify them, 

 and such modifications will be transmitted to their 

 offspring. 



It is obvious that if such were not the case 

 there could be no change in the structure or con- 

 stitution of any given line of organisms from the 

 remotest ancestor to the most recent descendant, 

 inasmuch as the hereditary and permanent altera- 

 tions of the body-plasm are contingent accord- 



[266] 



