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THE AMERICAN NATURALIST [Vol. LY 



gainotc'S or ni the ombryo. The fact that m vegotatively 

 propas^ated Mucors (3) I have found mutations relatively 

 common where the possibilitv of sexual reproduction was 

 ruled out, indicates that sudden genetic changes are not 

 necessarily associated with sexual processes. 



It has not been possible in this brief presentation to 

 give an extended classification ot mutations, nor to dis- 

 cuss in detail their ])ossible significance m evolution. It 

 will be sufficient if I have made clear the distinction which 

 must be kept m mind, in any discussion of the subject, 

 between mutations in individual genes and those brought 

 about by chromosomal aberrations. 



