COLOR AND COAT CHARACTERS. 41 



lack it, just as a heterozygous rough guinea-pig has been demonstrated 

 to do. 



No further matings of rough animals were made. It may be expected 

 that heterozygotes mated inter se would produce 3 rough : 1 smooth. 



SMOOTH ANIMALS MATED INTER SE. 



Without giving tedious tables, it may be stated that at least 1,500 

 smooth-coated hybrids have been born from smooth animals mated 

 inter se. These range from the ^ wild through eight subsequent gen- 

 erations. All smooth recessives extracted from rough crosses have 

 also bred true; there is no reversal of dominance, even though the 

 rough guinea-pig is very incompletely dominant over the smooth wild 

 C. rufescens. 



9. OTHER COLOR AND COAT CHARACTERS. 



UNIFORMITY AND SPOTTING. 



In guinea-pigs, the dominance of the uniform or self-colored coat 

 over a spotted coat is not so clear and well marked as the dominance of 

 other epistatic characters over their allelomorphs, nor is the segregation 

 of self-colored and spotted coats in the F2 generation perfectly evident. 



Rabbits likewise do not show a complete dominance of self-color over 

 Dutch markings; but Hurst (1905) reports that segregation takes place, 

 giving a ratio of 1 self : 2 imperfect dominants : 1 Dutch marked. If, 

 in rats, we consider the hooded pattern as a sort of spotting, then its 

 allelomorph is dominant and segregation is clear, though not complete. 

 In mice, the self-colored varieties are held to be dominant to spotted 

 varieties and segregation takes place, but Miss Durham (1908, 1911) 

 has recently reported a ''piebald" type which is dominant over self- 

 color. The whole question of spotting and its inheritance in guinea-pigs 

 is more unsettled than in any of the other rodents. 



Among guinea-pigs, two kinds of spotting are known. They are, 

 (1) the brindled type, in which black, red, and sometimes white hairs 

 are scattered over the body in a sprinkled fashion; (2) the ordinary 

 spotted varieties, in which uniformly colored spots of considerable size 

 occur on the head, shoulder, side, and rump. The spots in this latter 

 type may occur on one or a number of these regions. Since the purpose 

 of this paper is to compare the hybrids with tame guinea-pigs, I shall 

 only attempt to show that similar varieties of spotted hybrids can be 

 produced in both cases. 



The wild C. rufescens were all self-colored. In mating the wild males 

 to the tame female guinea-pigs three spotted dams were used. The 

 matings resulted in 5 self-colored ^ wild hybrids. Of these ^ wild 

 hybrids, only 2 were bred ( 9 75 and 9 118). One, 9 118, was bred to 



