CHAPTER VI 



THE BIOLOGICAL IMPORTANCE OF AMPHIMIXIS 



The more ancient an organic character is, the more persistent is 

 it. The characters of a genus are more persistent than the 

 characters of a species, and the characters of a species more per- 

 sistent than individual characters. This implies that the deter- 

 minants of a given organic character are more or less numerous 

 according as this character is more or less old. A recent adapta- 

 tion to new conditions has as its antecedent condition a corre- 

 sponding change in a majority of determinants in a majority of 

 ids ; but there may remain a strong minority of unchanged 

 determinants ; and should the conditions be unstable, an oscilla- 

 tion in the germinal nutrition may bring the determinants of the 

 new variation once more into a minority. On the other hand, 

 the determinants of a character which has long been adapted 

 have gradually gained so great a preponderance, and have so enor- 

 mously increased their assimilating power at the expense of that 

 of their neighbours, that such a character, even if its environment 

 change, may nevertheless continue for a long time unchanged. 

 An instructive example of this persistence of long-established 

 and firmly rooted characters is furnished by various species of 

 wild plants placed under domestication. Such a wild plant may 

 resist, during several successive generations, all the influences 

 of greatly modified conditions, and remain unchanged ; only 

 after a prolonged period do a few variations begin to manifest 

 themselves. The determinants of the original constitution of the 



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