DOMINANCE 



rates B from R. That division accordingly 

 may occur either so as to form gametes B and 

 R A respectively, or what is equally probable, 

 so as to produce gametes B A and R. Obser- 

 vation confirms this interpretation, for it is 

 found that the reversionary agoutis do not 

 breed true, but produce young of the three 

 sorts, agouti, black, and red, as expected. We 

 expect black individuals from unions of B with 

 B, or of B with R; we expect red individuals 

 from unions of R with R or with R A, and 

 from unions of R A with R A ; we expect agoutis 

 to be produced by any gametic union which 

 brings together the three factors B, R, and A. 

 There are six chances in sixteen for the oc- 

 currence of such a union, when the rever- 

 sionary agoutis are bred together. In fact, 

 however, agoutis are produced much oftener. 

 Approximately nine out of sixteen of the 

 young have been found to be agoutis. The 

 unexpected excess of agoutis in our experi- 

 ments was fully explained when these second- 

 generation agoutis were tested individually. 

 It was then found that they are of four sorts 

 as regards breeding capacity. The first sort 



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