No. 510] HEREDITY AND VARIATION 327 



tion may occur, if we hold that one of these races has 

 arisen from another. 



We find then that by selection we can isolate many 

 races of different mean size, and that the relative mean 

 size is inherited in each race. 



I Jul another fact of equal importance comes forth. 

 Within each race (derived from a single parent) the size 

 of the different component individuals varies extremely. 

 The. largest specimens of a given race are more than twice 

 as long as the smallest specimens, and every intermediate 

 dimension occurs. We may therefore represent the com- 

 position of a single race by the diagram of Fig. 4. These 



varying sizes within the single race inherited? Will 



