814 Fluctuations 



lief. It further reasons that a direct apprecia- 

 tion of the capacity of inheritance can only be 

 derived from the observation of the inheritance 

 itself. Hence it concludes that the average 

 value of the offspring is the only real standard 

 by which to judge the representatives of a race 

 and to found selection upon. 



These statements are so directly opposed to 

 views prevalent among plant-breeders, that it 

 seems necessary to deal with them from the 

 theoretical and experimental, as well as from 

 the practical side. 



The theoretical arguments rest on the divi- 

 sion of the fluctuating variability into the two 

 large classes of individual or embryonic, and of 

 partial deviations. We have dealt with this di- 

 vision at some length in the previous lecture. 

 It will be apparent at once, if we choose a defi- 

 nite example. Let us ask what is the real sig- 

 nificance of the percentage-figure of a single 

 plant in sugar-beets. This value depends in 

 the first place, on the strain or family from 

 which the beet has been derived, but this pri- 

 mary point may be neglected here, because it 

 is the same for all the beets of any lot, and de- 

 termines the average, around which all are fluc- 

 tuating. 



The deviation of the percentage-figure of a 

 single beet depends on two main groups of ex- 



