30 TYPES OF MENDELIAN HEREDITY 
in others the eye is nearly as narrow a bar as that of 
pure stock. In the male, which has one factor for 
bar eye, the eye is as narrow as in the pure (‘.e., 
homozygous) female with two factors. The inter- 
mediate condition in the female which is hybrid 
(heterozygous) for this factor is hence not explained 
by the lesser effect of the single factor, but is probably 
due to the competing influence of the other allelo- 
morph. Of course it might be contended that since 
in the male there is a different chromosome complex 
(XABCD YABCD) from that in the female XABCD- 
XABCD) it is this difference in other factors that 
causes the heterozygous female to have a wider eye 
than the male; but this argument is rendered improb- 
able here, when we recall that in only one out of many 
cases of sex linked inheritance, in which the hetero- 
zygous female is intermediate, is the male different 
from the homozygous female. 
In other cases the influence of one of the parents 
of the cross may be so slight as to escape detection 
on ordinary observation, and may require special 
measurements for demonstration. When flies with 
miniature wings (Fig. 16) are mated to wild flies, 
the daughters have long wings, which Lutz has shown 
to be a little shorter in proportion to the length of 
the legs than are the wings of wild females; but the 
difference is so slight that it could not have been 
detected without biometrical methods. 
Finally, we must consider the class of cases in 
which complete dominance has been described. All 
the cases. given by Mendel in peas were supposed 
