524 Influence of Nutrition and Selection. 



The experimental part of the work is to provide the 

 nutrition, i. e., generally favorable conditions of culti- 

 vation. The results, however, have to be dealt with by 

 statistical methods which were originated by Quetei.et 

 and Galton^ and have been developed in recent years 

 amongst others by Pearson, Ludwig, Duncker, Daven- 

 port and Amann.^ 



Let us begin with the latter point and let us seek to 

 delineate the main features of this method in a few short 

 paragraphs in order that we may have a clear idea of the 

 manner in which they are employed. I have chosen Gal- 

 TON^s method as the simplest and most convenient for the 

 latter purpose. 



Ouetelet and Galton have shown that the indi- 

 vidual variations of men and other animals follow the 

 laws of probability. The deviations from the type of any 

 fluctuating character can be expressed by a curve since 

 they are grouped symmetrically round the type as a center 

 of greatest density. The more numerous the observa- 

 tions the more exactly does the curve of variability coin- 

 cide with the curve of probability. The cause of this 

 parallel is, pretty obviously, that the various deviations 

 from the normal are determined by a vast number of ex- 

 ternal and internal influences. 



Quetelet asserted that the above law applied to 

 plants and Galton demonstrated it by a few experi- 

 ments. My cultures of races and varieties extending, as 

 they have done, over many years, have given me plenty 



^ Galton's Natural Inheritance is indispensable for a proper 

 understanding of the foundations of this method and the reader is 

 advised to refer to it in conjunction with this chapter. 



^My experiments were made in 1892- 1894, i- e., before the pub- 

 lications of these authors had appeared. 



