Experimental Hybridizing 93 
-albino, descended (extracted) from an animal with a uniform 
coat, one might be led to suppose that the white of the albino 
might go to augment the white of the spotted parent, but on the 
contrary these hybrids are uniformly colored. In the next gen- 
eration the two characters, U and S, separate, i.e. disjunct, 
and the offspring give the Mendelian proportions U+2US 
+S, i.e. one spotted to three uniform. 
Il. Cross between Two Forms unequally spotted with White. — 
If a much-spotted individual is bred to one very little marked 
with white, having for example only a little white at the end 
of its tail, the offspring shows that the maximal dark mark- 
ing is the dominating character. All the young have the tail par- 
tially white, but no other white marks on the body. Yet these 
young are not all exactly like the darker parent, since the degree 
of tail marking, for example, may be quite variable. In the 
next generation, when the young are inbred, the phenomenon 
of disjunction appears. Two groups of offspring arise, one 
oscillating around the least amount of white (one grandparent 
type), the other around the most white-spotted type (the other 
grandparent type). 
III. Cross between Two Much-spotted Forms. — Without ex- 
ception the young are spotted, but in variable degrees. The 
cross may even produce albinos if the two parents are hybrids, 
including the character A. These albinos, in turn, possess la- 
tent the spotted character. 
Progression of the Spotted Condition by Selection. — Beginning 
with mice little marked with white and excluding in each gen- 
eration the less-marked individuals, Cuénot found that the white 
areas could be increased slowly but regularly, so that in two 
and a half years mice were obtained that contained much white, 
and differed to a large extent from the first forms used. The 
details of the spotted type seem not to be represented in the 
germ-plasm, because the young and the parents are not identi- 
cal. Local factors appear to determine the limits of variation. 
In regard to the characters of albinos, it has been ‘pointed out 
that they carry in a latent form the characters of the race from 
