472 H. J. MULLER 
event which produces the mutation is therefore exceedingly 
localized 
8. The variations of the locus W are not distributed, as regards 
magnitude, in a ‘curve of probability.’ If anything, the extreme 
variations are most frequent, and minute variations are probably 
infrequent. Selection concerned with this locus alone would 
not be cumulative in its effect. 
9. The mutations of W are not quantitative variations of the 
entire gene; this is shown by a comparison of the eye colors of 
males with those of heterozygous and homozygous females. 
