238 MULTIPLE FACTORS 
“without,” race gave curve a in Fig. 59B, and 
2,538 of the “with” race gave curve b; it will be 
seen that these curves overlap. The 2,587 F, gave 
curve c, which shows the effect of incomplete 
dominance, together with a degree of dispersion 
about equal to that of the parental “with” race. 
The 3,100 F, gave curve d, which at first sight 
might be taken to indicate factor variability or the 
effects of recombination of numerous factors. 
Fig. 59A.—Grades I to X, showing “without” to “with” patterns 
on thorax of Drosophila. 
Curve e, however, shows the resultant which would 
be obtained by a combination of curves a, ¢, and b 
in a 1:2:1 proportion; the close similarity of this 
to the observed F, curve shows that the latter 
really represents a monohybrid Mendelian result. 
Had more factors been concerned, the deviation of 
the observed curve from the calculated would have 
been of a different type from that which occurred— 
fewer flies resembling the grandparents would have 
appeared rather than more, at least in the case of 
