SHULL: DUPLICATION OF A LEAF-LOBE FACTOR 



437 



Table 5 



Composition of F3 Families from F2 Parents Having B Lobes in Crosses betvjeen B. 

 Heegeri simplex and a Biotype of B. hursa-pastcris heleris from Tucson, Arizona 



zygous state, /. e., BbB'b' ; while 7 families gave ratios which may be 

 appropriately referred to the 3 : i group, indicating that the parents 

 of these had but one of the B factors and this one heterozygous, e. g., 

 Bbb'b' or bbB'b'. According to theoretical expectation for the number 

 of families given in Table 5 these three groups should occur in the ratio 



^ The occurrence ot one simplex in this family is of unknown significance. It 

 may represent an unusually defective 15 : i ratio, but the deviation is so much 

 greater than in any other family that other possibilities seem more likely to be true. 

 From all my experience with these pedigrees, it seems probable that this "simplex" 

 individual is merely a rhomboidea modified by the suppression of the B lobing. There 

 remain also the possibility of "loss mutation" and of a technical error. 



