LUTHER BURBANK 



And if such variations are the natural result 

 of the operation of the laws of heredity when 

 closely similar individuals, ranked as of the same 

 kind or species, are mated, it seemed reasonable 

 to expect that still wider divergencies and diver- 

 sities must be brought about in the offspring of a 

 union between individuals so conspicuously dis- 

 similar as to be ranked as members of different 

 species. 



Part of this, to be sure, was matter of com- 

 mon knowledge; for certain examples of the hy- 

 bridizing of species in the animal world has long 

 been familiar, the case of the mule being perhaps 

 the most striking one under every-day observa- 

 tion. But this particular case illustrates the union 

 of species that have become so widely divergent 

 that nature appears to put a ban upon their union; 

 permitting, indeed, the birth of offspring, but 

 condemning the offspring to infertility. The in- 

 ference that this case typifies the result of the in- 

 terbreeding of species is utterly misleading. 



To be sure, the tendency to erect barriers be- 

 tween species is obvious enough, for everyone 

 knows that most of the others among our domes- 

 tic animals cannot interbreed at all. But, on the 

 other hand, if species are really only races di- 

 verged from a common origin, as Darwin thought, 

 then there must have been a time when those 



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