INEQUALITIES IN HOMOLOGOUS CHROMOSOMES 123 
It has been shown by Castle (11) and others that in mice, 
rabbits, and guinea-pigs the ordinary gray color of the wild rodent 
is not a simple character, but on the contrary, is very complex. 
It depends—for example, in mice—upon the simultaneous 
presence of at least seven or eight color factors. The complete 
dropping of any one of these from the germ plasm modifies the 
color of the animal. 
The factor most commonly dropped is that for the production 
of color, the animal—whether potentially gray, black, or brown, 
ete.—being an albino, actually without color. The next factor 
very commonly dropped is that for barring of the fur. This 
does not show unless black or brown pigment is present in the 
hair. The barring of the hair is due to the fact that some factor 
prevents the development of black and brown pigment granules 
in a portion of the individual hair immediately below the tip, 
leaving a black tip and a dark base with a light yellow band be- 
tween them. When this barring factor is dropped, we get a black 
or a brown animal instead of a gray. The next most commonly 
dropped factor is that for the production of black, giving cinna- 
mon or brown animals. By dropping the factor for self color, 
spotting results, spotting of two sorts, white upon a-golored coat, 
or yellow upon a black, brown, or gray coat,--giving in the 
extreme cases white with black or brown eyes find yellows with 
black or brown eyes. By dropping the dark-é¥ed character we 
obtain pink-eyed animals with a scarcity of pigment in the fur. 
By dropping the intensity-of-pigmentation factor we get dilute- 
ness of pigment, giving dilute-pigmented gray, black (‘blue’), 
brown (‘cream’), or yellow animals. When all of these factors 
are present we have the wild gray type. By the dropping of 
any one of them entirely the color may be modified accordingly. 
It is evident that these animals lack something. The dropping 
of the black pigment, for example, gives animals which are 
cinnamon or brown. No black can be produced in the race 
until this factor is again added to the mixture. It is entirely 
absent. In this case black cannot be considered a latent char- 
acter which has been restricted in some way from attaining its 
development, as is the case in albinos of gray or black animals; 
JOURNAL OF MORPHOLOGY, VOL. 26, No. 1 
