THE ABSENCE OF DOMINANCE 61 



and that the largest of these is the hybrid group over 

 again while the others are the original parent groups. 

 Clearly this is a similar case, excepting that neither black 

 nor white is dominant the one to the other and the hybrid 

 is something intermediate between them. Thus there is 

 only one pair of characters in operation. 



Although it is obviously sound, it may be well to show 

 that this hypothesis can be proved. If there were more 

 than one pair of factors, say two, namely, X and x and 

 Y and y, the constitutions of the hybrids and the two 

 parents should be : 



Whites 



XX 



YY 



Then, if the hybrids were mated with their black parents, 

 the materials offered should be : 



By the Hybrids By the Blacks 

 X X 



.X X. 



•Y y. 



■y y- 



and equal numbers of the following four kinds of progeny 

 should be produced, three of which should be hybrid in 

 one or in both pairs of characters : 



XX XX Xx Xx 



Yy yy Yy yy 



Instead of this, however, only two kinds were produced, 

 namely, 27 blue hybrids and 19 true-breeding blacks. 



