COLOR AND COAT CHARACTERS. 43 



sires belong to a brindled race, but are not known to carry dilution. 

 This brindled race of guinea-pigs produced reds, but no creams, when 

 mated inter se. It is not a matter of certainty that the brindled males 

 are entirely or even partly responsible for this extreme dilution. No 

 solution has yet been possible. It is possibly another of the unexpected 

 disturbances which hybrids are prone to show, but for which we know 

 no cause. Cavia rufescens itself was of intense pigmentation. 



LONG HAIR AND SHORT HAIR. 



The pure wild stock was short-haired. No experiments have been 

 made to test whether this short-haired condition of the wild is dominant 

 to the long-haired condition of the tame, just as is the case in guinea- 

 pig matings. 



One peculiar character may be recorded here. The wild Cavia 

 rufescens has very straight, coarse, bristly hair, which tends to stand 

 erect, particularly on the head and neck (fig. 1). The ^ wild hybrids 

 had hair intermediate in texture between that of the respective parents, 

 but approaching the guinea-pig more nearly than the wild parent. The 

 approximation to the guinea-pig increased in later generations, so that 

 no clear distinction could be made between the hybrids and guinea-pigs 

 in this particular. 



10. THE FERTILE HYBRID MALES IN COLOR CROSSES. 



All the data which have formed the basis for the study of color 

 inheritance were accumulated from the matings of the wild males with 

 guinea-pigs, or from the matings of hybrid females with guinea-pigs. 

 The result has been to establish sets of allelomorphic pairs and domi- 

 nance and segregation, comparable to that which occurs in ordinary 

 guinea-pig matings. The conclusions are subject to one limitation, 

 for the hybrid females were continually mated to guinea-pigs and no 

 data were presented on hybrids mated inter se. This restriction is not 

 a serious one, for it has been proven that the female hybridfe are 

 similar to the guinea-pig in color transmission. Now, it is well known 

 that sex does not affect the gametic or zygotic color formulae in guinea- 

 pigs; hence we have assumed that the sex of the hybrids makes no 

 difference, and that the results obtained from female hybrids would be 

 duplicated by those from fertile male hybrids. 



Recently, fertile males have been obtained by reduction of wild blood, 

 i. e., by continually mating the female hybrids back to the guinea-pig. 

 A fuller discussion of these results will follow; but at this point it is 

 appropriate to discuss briefly the relation of fertile hybrid males to 

 color inheritance. 



