No. 555] SIMPLIFICATION OF MEN DELI A N FORMULAE 179 



6. p = pink-eyed. 



7. s = spotted. 



8. Y— yellow. 



The a mutation, however combined, if present in a homo- 

 zygous condition, prevents the development of pigment 

 in the skin, hair or eyes. The d mutation, under like cir- 

 cumstances, makes the pigmentation of the coat dilute, or 

 pale; the p mutation reduces even more strongly the pig- 

 mentation of coat and eyes alike, but does it in a different 

 way; the s mutation causes pigment to be altogether want- 

 ing in certain areas of the coat more or less definite in 

 position and extent, which areas accordingly appear as 

 white spots. 



Combinations of these four mutations present no diffi- 

 culties of description or recognition, though breeding 

 tests alone suffice to differentiate the several sorts of 

 albinos, since all look alike. The nomenclature also is 

 perfectly simple. Thus, 



«p = albino transmitting the pink-eye mutation in 

 crosses. 



adp = albino transmitting both dilution and pink-eye 

 in crosses, etc. 



Combinations of b, c, and Y, one with another, form the 

 fundamental and best known color varieties, which will 

 now be considered. 



In the b mutation, the fur is black ; in the c mutation, 

 it is brownish gray, called cinnamon. In the Y mutation, 

 the coat is yellow. Of the several mutations mentioned, 

 Y alone is dominant over the wild gray, but it occurs only 

 in a heterozygous state, and hence never breeds true. 



The complete color series involving these three muta- 

 tions, but excluding all others, is as follows: 



Wild = gray. 



b = black. 



c = cinnamon. 



be = black-cinnamon (chocolate). 



Y = yellow (giving also gray offspring). 



&r= black-yellow (giving also black offspring). 



