MULTIPLE FACTORS 239 
one of the two grandparental types. As to the 
exact way in which the curve of the F, individuals 
in a case of multiple factors will differ from that in a 
monohybrid cross like the above, no definite rule 
can be formulated; the result will vary according 
to the number and mode of interaction of the 
multiple factors, but in any event the presence of 
the multiple factors may be detected by comparing 
Fer - 
cent 
ip 
10 fi \ S = 
ME [| SX Ks 
y) y. ~. 
/ ‘. ~s, 
if “Ss ts 
‘ ~h. was 
Grad 
Cea I 0 Ww y uw WwW Ww 16 x 
Fig. 59B.—Curves representing the distribution of grades of the 
trident pattern ‘‘with’’ in various stocks and crosses. 
the observed curve with the one calculated from the 
parental and F, curves by the method used in the 
above experiment. The two curves should never 
be the same, and the multiple factor curve will 
almost always show a smoother, more even distri- 
bution, with less tendency to form a mode at each 
grandparental value. 
In distinction to cases of single factor-differences, 
it should also be noted that in cases of multiple 
