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THE AMERICAN NATURALIST [Vol. LV 



plant and most of them are obviously detrimental. More- 

 over, if variations occur at random the chances are almost 

 infinitesimal that any particular variation would consti- 

 tute a favorable addition to the complex mechanism of a 

 highly specialized plant or animal. A chance alteration 

 in the parts of a machine would seldom improve its 

 efficiency. 



Of the recorded heritable variations in maize the de- 

 parture from the normal condition is recessive in a great 

 majority of the cases. Aside from a number of wide- 

 spread characters where neither member of the allelo- 

 morphic pair may be considered more normal than its 

 mate, the only dominant variations in maize that come to 

 mind are pod com and fasciated or bear's foot ears. 



On the other hand, the recessive variations already 

 described number more than 20 and it would be safe to 

 say that hundreds of others are known to maize breeders. 



In a complex organism we may expect that deleterious 

 variations will occur more frequently than beneficial 

 variations, but that such a large proportion of the char- 

 acters should be recessive calls for comment. East and 

 Jones hazard the suggestion that natural selection has 

 suppressed the tendency to produce dominant unfavor- 

 able variations while the tendency to produce unfavor- 

 able recessive variations has been tolerated. 



It should be kept in mind that the observed preponder- 

 ance of recessive characters does not necessarily imply 

 that a corresponding preponderance of mutations or 

 germinal changes are recessive. Dominaint disadvaji- 

 tageous variations are eliminated much more promptly 

 than recessive and the gradual accumulation of recessive 

 characters soon would place them in the majority in any 

 cross-bred species. It seems not improbable that the 

 great preponderance of recessive over dominant char- 

 acters is a measure of the extent to which dominant char- 

 acters are eliminated. In a cross-bred form even varia- 

 tions that result in sterility or death may persist indefi- 

 nitely if recessive. It may well be that the rate at which 



