ON THE QUICK GROWING WALNUT 



to it. But it is equally obvious that there are vast 

 numbers of other heritable characters regarding 

 which no such clear matching as to dominance and 

 recessiveness is observed to take place. 



And so the early enthusiasts were led finally to 

 see that Mendelian dominance and recessiveness 

 apply only to a certain small number of hereditary 

 factors in the case of any individual plant or 

 animal. 



They came presently, after much heated argu- 

 ment, to admit that dominance and recessiveness 

 constitute after all only a minor aspect of Men- 

 delian heredity. 



Yet this aspect of the subject, even if not all- 

 important, has obvious interest. And the question 

 naturally arises as to which ones among the num- 

 berless hereditary factors in the case of any given 

 organism will "Mendelize" in this sense, and why 

 these factors will thus Mendelize while others fail 

 to do so. 



The answer is found, apparently, in the simple 

 assumption that the factors that show the phenom- 

 ena of dominance and recessiveness are those that 

 are relatively new acquisitions in the germ plasms 

 of the species under observation. Traits that have 

 been the common heritage of the ancestry for un- 

 told generations, constituting the fundamental 

 structures of the organism, do not Mendelize. They 



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