1 6 Heredity and Eugenics 



are in e^'ery direction; and orthogenesis with those small 

 or large and relatively few variations which for some reason 

 persist and increase from generation to generation and carry 

 forward the group as a whole. 



4. BIOMETRY 



When the idea of natural selection became dominant, 

 and new species were believed to have arisen by the accumu- 

 lation of small variations, which seemed to be indeiinite 

 and fluctuating, a statistical method of attack began to be 

 developed, a method that has been named biometry. The 

 most conspicuous names that one meets in the literature of 

 biometry are Galton, the English pioneer in the exploitation 

 of the method; and Pearson, who has been largely instru- 

 mental in carrying it forward into its more advanced 

 mathematical stage. 



It is a method that deals with groups or populations, 

 rather than mth individuals, and its results present the 

 averages of variations. It is evident that an average 

 obtained from the measurements of a given character in a 

 series of individuals will depend upon the individuals 

 selected for measurement. Therefore, biometry demands 

 to an unusual degree the elimination of preconceived opin- 

 ions and the exercise of great judgment. It has become 

 so special and intricate a method that it can be followed, 

 with full understanding, only by those with special training; 

 so that any adequate illustration of it will be left to such of 

 the subsequent addresses as may have occasion to apply it. 



A word can be said, however, concerning its use as an 

 instrument in the study of the processes of evolution. 

 Selecting any character or group of characters that are to 

 be measured or counted, and using a wisely selected range of 



