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 Cu^not'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 



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^A B!-TYPE BRACHYPHALANGOUS INDIVIDUALS 



CT© B- TYPE BRACHYPHALANGOUS 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_ 



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 Q^ INSUFFICIENT INFORMATION 

 @^ 6-TYPE BRACHYPHALANGOUS INDIVIDUALS 

 Cf CT Cf' ©^ B!-TYPE BRACHYPHALANGOUS INDIVIDUALS 



Text-figure 4. — Pedigree demonstrating the distribution of B-t3T)e and B !-type 

 brachyphalangy among the descendants of 19.4 9 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. 



