INHERITANCE OF ACQUIRED CHARACTERS 81 



is apparent that only the "born" ones can be, which 

 have their roots in the germplasm whence the new 

 individual arises, and that "achievements" and 

 "thrusts," in order to reappear in the succeeding gen- 

 eration, can do so only by first becoming incorporated in 

 the germplasm. 



Any character that is not acquired must have been 

 present in the germplasm from which the organism 

 arose, as there is no transfer of characters between 

 organisms except through the germ-cells. Thus it is 

 evident that the only inherited acquisitions are those 

 which, either primarily or secondarily, bring about 

 variation in the germplasm. Such temporary acquisi- 

 tions as a coat of tan or a display of freckles do not 

 impress the germplasm, for when the cause that in- 

 cites their appearance is removed, they soon vanish. 



9. WHAT MAY CAUSE GERMPLASM TO VARY OR TO 

 ACQUIRE NEW CHARACTERS? 



The causes which bring about changes in the germ- 

 plasm may be either internal or external. 



Of possible internal causes may be mentioned first 

 the "amphimixis" of Weismann, that is, the mixture 

 of two nearly related strains of germplasm in sexual 

 reproduction within a species, or secondly, the mixture 

 of two more remotely related strains resulting in hy- 

 bridization. In either case the strain of germplasm 

 undergoes a shake-up that may result at least in new 

 combinations of characters, if not in the production 

 of entirely new characters. This recombination of 



