PHENOMENA OF INHERITANCE 227 



herited or not, our study of inheritance can 

 only end in confusion. The value of statistics 

 depends upon a proper classification of the 

 things measured and enumerated, and if 

 things which are not commensurable are 

 grouped together the results may be quite 

 misleading and worthless. Unfortunately 

 Galton and Pearson, as well as some of their 

 followers, have not always carefully distin- 

 guished between hereditary and environmental 

 characters. Furthermore much of their ma- 

 terial was drawn from a general population in 

 which were many different families and lines 

 not closely related genetically. Consequently 

 their statistical studies are of little value in dis- 

 covering the physiological principles or laws 

 of heredity. Jennings (1910) well says, 

 "Galton's laws of regression and of ancestral 

 inheritance are the product mainly of a lack 

 of distinction between two absolutely diverse 

 things, between non-inheritable fluctuations 

 on the one hand, and permanent genotypic 

 differentiations on the other." In the case of 

 man we have few certain tests to determine 

 whether the differential cause of any character 



