HEREDITARY TYPE OF CHARACTER STUDIED. 



57 



Our knowledge of modifying genes in a more general sense of the 

 word may be said to date back to Cuenot's investigation of the intensi- 

 fying and diluting genes influencing the effect of other color factors in 

 mice (1907). The perception of their widespread occurrence and of 



11.5 



NORMAL INDIVIDUALS 



INSUFFICIENT INFORMATION 



BI-TYPE BRACHYPHALANGOUS INDIVIDUALS 



B- TYPE 6RACHYPHALANGOUS INDIVIDUALS 



TEXT-FIGURE 3. Pedigree demonstrating the distribution of B-type and B !-type 

 brachyphalangy among the descendants of ll.Scf C.A.B.H., line 1. 



19.4 



cff 90*9 tftj> QcT QC? QC? f cTT 



FAMIUT 



QQ 



NORMAL INDIVIDUALS 



INSUFFICIENT INFORMATION 



B-TYPE BRACHYPHALANGOUS INDIVIDUALS 



BI-TYPE BRACHYPHALANGOUS INDIVIDUALS 



TEXT-FIGURE 4. Pedigree demonstrating the distribution of B-type and B !-type 

 brachyphalangy among the descendants of 19.4 $ L.E.O., line 9. 



their importance grew gradually out of the discussion on the multiple- 

 factor view, inaugurated by the investigations of Nilson-Ehle (1909) 

 and East (1910, 1911). East gives (1912) a very clear discussion of the 

 "modifying factors," and in recent years they play the foremost part 

 in all publications dealing with the question of the effect of selection. 



