INFLUENCE OF ENVIRONMENT 359 



the same rank of society and in the same 

 country." 



The part played by these different factors 

 of development may be graphically illustrated 

 by the accompanying diagram (Fig. 83), in 

 which the base line represents heredity and 

 the other lines represent the extrinsic factors 

 of environment and education. For each in- 

 dividual heredity is a constant factor but en- 

 vironment and training are variables. With 



Heredity 



FIG. 83. Diagram to show the influence of heredity, en- 

 vironment and training in the development of an individual. 

 Various types of individuals (represented by the triangles) 

 may be produced from the same germ cells (heredity) if the 

 environment and training are variable. 



