MULTIPLE FACTORS 



239 



one of the two grandparental types. As to the 

 exact way in which the curve of the ¥■> 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 



Per 

 cent 



35 

 30 

 25 

 20 

 15 

 10 

 5 



Grade ] 

 Centers 



m 



W 



21 



M 



M 



K 



Fig. 5913. — Curves representing the distribution of grades of the 

 trident pattorn "with" in various stocks and crosses. 



the observed curve with the one calculated from the 

 parental and Fi 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 



