238 



MULTIPLE FACTORS 



''without," race gave curve a in Fig. 59J5, and 

 2,538 of the "with" race gave curve b; it will be 

 seen that these curves overlap. The 2,587 Fi 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 Fo gave curve d, which at first sight 

 might be taken to indicate factor variability or the 

 effects of recombination of numerous factors. 



Fig. 59 A.— 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, c, and b 

 in a 1 : 2 : 1 proportion; the close similarity of this 

 to the observed Fo curve shows that the latter 

 really represents a monohybrid Mendehan 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 



