4 GENETICS 



in the long run. Improved environment and educa- 

 tion may better the generation already born. Im- 

 proved blood will better every generation to come. 



What, then, is this "blood" or heritage? Ex- 

 actly what is meant by heredity ? 



2. A DEFINITION OF HEREDITY 



Professor Castle, in his recent book on " Heredity 

 in Relation to Evolution and Animal Breeding," has 

 defined heredity as " organic resemblance based on 

 descent." The son resembles his father because he 

 is a "chip off the old block." It would be still 

 nearer the truth to say that the son resembles his 

 father because they are both chips from the same block, 

 since the actual characters of parents are never trans- 

 mitted to their offspring in the same way that real 

 estate or personal property is passed on from one 

 generation to another. When the son is said to have 

 his father's hair and his mother's complexion it 

 does not mean that paternal baldness and a vanish- 

 ing maternal complexion are the inevitable conse- 

 quences. 



Biological inheritance is more comparable to the 

 handing down from father to son of some valuable 

 patent right or manufacturing plant by means of 

 which the son, in due course of time, may develop an 

 independent fortune of his own, resembling in charac- 

 ter and extent the parental fortune similarly derived 

 although not identical with it. 



So it comes about that "organic resemblance" 



