CHAPTER XVII 



HERITAGE OF THE INDIVIDUAL 



The entire organism may be compared to a web of which 

 the warp is derived from the female and the woof from the 

 male. Huxley. 



THE old adage that ' like begets like ' expresses the general 

 fact of HEREDITY. Every one recognizes that parent and 

 offspring agree in their fundamental characteristics or 'be- 

 long' to the same 'species.' And every one realizes that the 

 resemblance may be strikingly exact even in details of form 

 or behavior. Family traits crop out. The mere statement 

 of striking resemblances among the individuals of a family 

 is a tacit admission that no two individuals are exactly alike; 

 in other words heredity is "organic resemblance based on 

 descent " - inheritance of the characters exhibited by the 

 parents is not complete, there is VARIATION. Indeed "varia- 

 tion is the most invariable thing in nature," but one must 

 guard against the impression that there is an antithesis 

 between heredity and variation. "Living beings do not 

 exhibit unity and diversity, but unity in diversity. In- 

 heritance and variation are not two things, but two imperfect 

 views of a single process." 



We must now address ourselves to the problems of heredity 

 and variation which are at the basis not only of what organ- 

 isms have been in the past and are at the present, but also 

 of whatever the future may have in store for them. Varia- 

 tions are the raw materials of evolutionary progression or 

 regression. From a broad point of view, the origin of 



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