200 DOMESTICATED ANIMALS AND PLANTS 
and which therefore may go on hidden for a time, only to sud- 
denly appear when the overshadowing dominant, for any reason, 
is absent. 
Separation of the desired character. The separation of the 
desired character from its entanglements with others is some- 
times easily effected, but more often with great difficulty, espe- 
cially when dominant undesirable characters are involved. As 
an example of easy separation take the following theoretical 
case: Suppose we cross the colors black and white. Under 
Mendel’s law we shall have offspring of the cross as follows: 
62 + 2 bw +, in which 2? is pure black, ze? pure white, and 
2 bw is mixed, black and white. In this particular case, there- 
fore, we shall find the offspring of three distinct colors, all of 
which are easily separable, one from the other. 
In the vast majority of cases, however, the characters do not 
blend in this way, so that the middle term does not stand out 
distinctly by itself. One of the characters generally overshadows, 
that is to say, is dominant over, the other, making it difficult, if 
not impossible, to separate by inspection the members of the 
middle term from the pure dominants; that is, to determine 
from a mixed population of offspring, arising from a crossed 
parentage, which ones are pure dominants and which are 
mixed, dominant, and recessive. 
Behavior of the recessive. It will be remembered that reces- 
sive characters appear unassociated with the dominant in 
one fourth of all crossbred individuals, after the formula 
D4+2Dr+7?, in which PD stands for dominant and 7 for 
recessive. For this reason it is comparatively easy to proceed 
when the character desired is recessive, because these individ- 
uals that seem to be recessive are really what they seem, pure 
recessive, and will breed pure. 
Behavior of the dominant. It is not so easy, however, with 
the dominant, when that happens to be the character in whose 
improvement we are interested. Because it is dominant it will 
appear not in one fourth but in three fourths of the offspring ; 
