THEORIES IN PRACTICE 383 



groups of characters in which the old guards, 

 so to speak, that have control over the funda- 

 mental characters are in conflict, no union is 

 possible. 



Either fertilization will not take place, or the 

 offspring will be sterile. Only within narrow 

 limits, and as regards the new and relatively un- 

 essential characters, can there be diversity or, at 

 most, the accentuation of old characters. 



Such an accentuation, for example, occurs, we 

 may suppose, in the case of the hybrid walnuts, 

 which take on gigantic growth. Both Persian 

 walnut and California walnut have in their germ 

 plasm the hereditary factors of large groups of 

 remote ancestors of the Mesozoic era, when 

 gigantism was the fashion, but these factors 

 have for long generations been subordmated by 

 newer one born in a less favorable era. Now, 

 however, hybridization brings the two strains 

 together, and the two dominant groups of 

 factors for slow and relatively dwarfed growth 

 in some way mask or neutralize each other, 

 enabling the earlier groups to make their 

 influence felt. 



And here, as we have seen, the factors for 

 growth that have thus been rudely disturbed as 

 to their hitherto harmonious coalitions, are re- 

 assorted in the second generation, as united 



