236 



Isabel AicCracken 



For the seventh generation data, the following mating cate- 

 gories were estabhshed. 



a AB xAB, of AB ancestry for six generations. 



b S xS of dominant S parents (dominant over AB). 



c BxB of incompletely dominant S parents, and S xAB 

 grandparents. 



d B xB of dominant B parents (dominant over AB). 



e AB xAB, extracted AB of S parents and S xAB grand- 

 parents. 



TABLE VI {Seventh Generation) 



*The ancestry of each parent is of similar character. 



Comparing sixth and seventh generations we find in the latter 

 the alternate B completely eliminated from the AB line (Table 

 ¥,/>, and Table VI, «). 



S in the second generation from hybrid S (Table VI, b) breeds 

 true as far as AB is concerned. Its dominance over AB is there- 

 fore progressive. There is a much more rapid elimination of AB 

 at this stage than previous breeding experiments have shown to 

 be the case with B. 



B in the second generation from hybrid B breeds true (Table 

 VI, d). Its dommance over AB is therefore also progressive. 



Extracted B from hybrid S breeds true at once (Table VI, c). 



