LUTHER BURBANK 



different from thorns and thistles, but the gradua- 

 tions of modification through^ which the trans- 

 formation has been brought about were infinitesi- 

 mal in any pair of generations and have produced 

 their effects only through the cumulative influ- 

 ence of myriads of generations. 



If really radical transformations could be 

 wrought in the germ-plasm of any organism in a 

 brief period of time, the whole organic world 

 would be topsy-turvy and there would be no laws 

 of heredity to discuss at least those laws would 

 be something quite different from what they are. 



Let us, then, supplement our idea of the con- 

 tinuity of the germ-plasm with the thought that 

 this germ-plasm may be modified from time to 

 time, but that the amount of modification permis- 

 sible within any limited period is infinitesimal in 

 comparison with the sum total of the qualities of 

 the germ-plasm itself ; which qualities, it may be 

 added, represent the aggregate influence of past 

 environments throughout vast and incomprehen- 

 sible periods of time. 



Luther Burbank has a capital phrase, to the 

 effect that "heredity is the sum of all past envi- 

 ronments." The import of the phrase becomes 

 perhaps clearer if we think of it in connection with 

 this picture of the ancestral germ-plasm the 

 tangible and definite series of cells directly link- 

 ing every individual of any generation with the 

 entire series of its direct ancestors. 



[268] 



