UNIT CHARACTERS OF DOGS 141 



either as a sport from the colored condition, or more probably 

 as an extreme form of white spotting. In this variety the eye 

 pigmentation is never entirely lost as in albino rodents; it is 

 largely retained, as is the case also in white cattle, horses and 

 swine. In crosses between the different colored breeds, 

 black-and-tan {i. e., bi-color black) is dominated by self black 

 and bi-color brown by self brown; black is dominant over 

 yellow (or red) and also over brown. As yellow and brown 

 are independent unit-character variations they may be com- 

 bined, a result seen in brown-eyed yellow dogs. Thus among 

 pointers (Little, 1914) or cocker spaniels (Barrows and 

 Phillips, 1915) a cross of black-eyed yellow with brown pro- 

 duces in Fi black dogs and in F2 blacks, browns, black-eyed 

 yellows and brown-eyed yellowsX The same result in both 

 Fi and F2 may be obtained by crossing black with brown- 

 eyed yellow. What appears to be self white, but is more 

 probably a very pale yellow, according to Barrows and 

 Phillips, has appeared in spaniels as a sport and is recessive 

 in heredity. Whether in other breeds self white is recessive 

 or dominant is not known at present. It is probable that in 

 some cases, as in bull terriers, it is only an extreme form of 

 white spotting, in which case we should expect the dominance 

 to be imperfect. A short stumpy tail is probably a dominant 

 unit-character variation in dogs, as it is in cats. 



/ 



^ In Dachshunds red is not uniformly recessive; it apparently may be dominant. 



