256 EFFECTS OF EXPOSING GERM-CELLS TO RAYS OF RADIUM 



tinue the observations over the second generation of both lib and I5« 

 broad x i$a narrow. It must be concluded, then, that most of the 

 variants were not true mutations, and that further evidence is needed 

 before we may say with entire confidence that mutation may be 

 induced by the stimulus of radium rays. 



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