50 



THE INHERITANCE OF COLOR IN MICE. 



In the following pages will be found a brief description of the various color 

 varieties, as they appear to the unaided eye, followed by a list of crosses made 

 with each color variety. In the tables it has been found expedient to use the 

 following abbreviations to designate in simpler form the color varieties, a list of 

 which has already been given: 



B = black, 

 Br = brown, 

 d = dilute, 



p = pink-eyed, 



Ag = a.goui\, 



W = white (albino), 



F= yellow, 

 sF= sooty yellow, 

 cF = cream yellow. 



Thus, for example, pdBAg is equivalent to pink-eyed dilute black agouti, color 

 variety No. 4 of the extended series. 



Unfortunately, in many of -the crosses the numbers of animals recorded 

 are small. Aberrations from the expected mendelian ratios of the color 

 classes may also be found in some cases; but an examination of these seems 

 to indicate that they would diminish with an increase in the number of animals 

 recorded. 



EXTENDED SERIES. 



I. Black Agouti, YBrBDPA (Fig. 1). 



The common coloration seen in the house-mouse (Mus musculus). Eyes black, ears darkly 

 pigmented, hairs on ventral surface tipped with dull-yellowish, then dark slaty to the 

 base. Tail dark-pigmented. Dorsal hairs tipped with black, then having a yellow 

 band and below that being slaty to their base. Such an arrangement produces the 

 "ticked" or "agouti" coat pattern. Tuft of hairs at the base of the ears yellowish — 

 a few light hairs on sides, iianks, and feet. Hairs around anus are Ught. 



Black agouti x black agouti. 



Cross 1. Giving only BAg young; therefore one of the parents, at least, may be considered 

 homozygous black agouti, type 1 (extended series). The animals used in this cross 

 were descended from yellows. 



Cross 2.^ Parents heterozygous in black. YoBriBDiPiAi x Y2Br2BDiP2A2. Expectation, 

 3 BAg to 1 BrAg. 



