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THE POPULAR SCIENCE MONTHLY 



stature of individual parents is shown by the oblique line, the stature 

 of children by the dotted curve, and the mean stature of the race in the 

 horizontal dotted line. 



One of the chief aims and results of statistical study is to eliminate 

 individual peculiarities and to obtain general and average results. 



Fig. 49. Diagram to Illustrate Three Kinds of Inheritance Described by 



Galton. (After Walter.) 



Such work may be of great importance in the study of heredity, espe- 

 cially where questions of the occurrence or distribution of particular 

 phenomena are concerned ; but the causes of heredity are individual and 

 physiological, and averages are of less value in finding the causes of 

 such phenomena than is the intensive study of individual cases. 



By observation alone it is usually impossible to distinguish between 

 inherited and environmental resemblances and differences, and yet this 

 distinction is essential to any study of inheritance. If all sorts of like- 

 nesses and unlikenesses are lumped together, whether inherited or not, 

 our study of inheritance can only end in confusion. The value of sta- 

 tistics 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. Unfortu- 

 nately Galton and Pearson, as well as some of their followers, have not 

 carefully distinguished between hereditary and environmental characters. 



