IMPORTANCE OF MODIFICATIONS 521 



re-impressed on each successive generation, and that detrimental 

 modifications be avoided. 



But the biological conclusion has to be in an important respect 

 corrected for the social realm, in view of the fact that man 

 has an external heritage of custom and tradition, institution 

 and legislation, literature and art, which is but slightly or not 

 at all represented in the animal world, which yet may be so 

 effective that its results come almost to the same thing as if 

 acquired characters were transmitted. They are re-impressed 

 on the bodies and minds of successive generations, though 

 never ingrained in the germ-plasm. It seems probable that 

 not a few of the biologically and socially unfit are only 

 modificationally veneered, or repressed, or arrested. 



Moreover, while among plants and animals the organism is 

 often largely a creature of circumstances, very thoroughly in 

 the grip of its surroundings and mastered by them, it becomes 

 otherwise as we ascend the scale of being. Increasingly we find 

 the organism — be it bird or mammal or man — much more master 

 of its fate, able to select its own environment in some measure, 

 able to modify its surroundings as well as be modified by them. 

 As we take a bird's-eye view of the course of evolution, must 

 we not recognise the gradual emergence of the free agent — the 

 operation of what has been badly called " organic selection " ? 



§ 4. Social Aspects of Heredity 



We have defined heredity as the genetic relation between 

 successive generations, and inheritance as all that the organism 

 is or has to start with in virtue of its hereditary relation to 

 parents and ancestors. All sociological talk that appeals to a 

 " principle," " law," or " force " of heredity should be ruled out 

 of court. 



The hereditary relation is sustained by the germinal material, 

 and the precise study of this physical basis has done much of 



