42 GENETICS 



4. METHODS OF STUDYING VARIATIONS 



Roughly stated, there are three ways of studying 

 variations : first, Darwin's method of observation 

 and the description of more or less isolated cases ; 

 V second, Gal ton's biometric method of statistical 

 inquiry ; and third, Mendel's experimental method. 

 The second of these methods will be considered in 

 this chapter. 



5. BIOMETRY 



The new science of biometry, that is, the applica- 

 tion of statistical methods to biological facts, has 

 been developed within recent years. Sir Francis 

 Galton, Darwin's distinguished cousin, may be re- 

 garded as the pioneer in this field of research, while 

 Karl Pearson and his disciples constitute the modern 

 school of biometricians. 



Although mathematical analysis of biological 

 data when not sufficiently ballasted by biological 

 analysis of the same facts may sometimes lead the 

 investigator astray, yet often the only way to for- 

 mulate certain truths or to analyze data of some 

 kinds is by resort to statistical methods. Biome- 

 tricians are quite right in insisting that it is frequently 

 necessary to go further than the fact of variation, 

 which may be apparent from the inspection of an 

 individual case, and to deal with cumulative evidence 

 as presented through statistical analysis. 



In matters of heredity, however, facts as they 

 occur in single cases and definite pedigrees seem to 



