64 INHERITANCE IN GUINEA-PIGS. 



COLOR VS. WHITE (1 A). 



Probably dilution of the type of the blue and dilute yellow mice and 

 rabbits and maltese cats belongs here, rather than in IB, since the 

 effect seems to be due to the distribution of pigment within the indi- 

 vidual hairs rather than to any effect on the actual pigment granules. 

 Most of the factors which belong hi this class, however, are those which 

 determine patterns of white as opposed to areas which are colored 

 under most combinations of other factors. In this class are such fac- 

 tors as on the one hand determine a self-colored coat, and on the other 

 black-eyed whites, as in mice; white patterns, as in hooded rats, Dutch 

 and English rabbits; or scattered white hairs, as hi silvered guinea- 

 pigs. In cases where several independently inherited white patterns 

 have arisen it is evident that there can be no single factor which alone 

 determines self. The "self " allelomorphs of the white-pattern factors 

 can merely be defined as conditions for self. Where more than one 

 white-pattern factor is present in an animal, combination patterns are 

 produced. 



Clear-cut Mendelian factors which belong to this group are known in 

 mice, rats, and rabbits, but none have been isolated in guinea-pigs, 

 although irregular blotching and silvering with white are common. The 

 symbol S will be used to represent an assemblage of unanalyzed factors. 



Stc, an assemblage of unanalyzed factors which determine white spotting. 

 INTENSITY OF GENERAL COLOR DEVELOPMENT (1 B). 



In this group fall albinism and its variations. These factors affect 

 all color, but not wholly irrespective of the kind of color. There are 

 several peculiarities which are discussed more fully in a later section 

 (page 70). The most important is the fact that the level of intensity 

 of the color factor at which yellow can develop at all is higher than the 

 threshold for black or brown. This does not affect the differentiation 

 of the fur into yellow and dark pigmentation areas by factors of group 

 2, but involves the result that with certain albino series factors, yellow 

 areas appear white, while dark areas are quite strongly colored. Indeed, 

 in albinism itself, dark pigmentation areas can often be distinguished 

 from yellow areas by a slight sootiness in the former, absent in the latter. 



C. Determines the highest intensity of color of skin, fur, and eye which is to be found with a 

 given array of other factors; dominant over Ca, CV, and C a , where distinguishable 

 in its effects. In the following table, and hi the similar tables under Cd, CV, and C a , 

 are given the ranges of intensity in the yellow, black, and brown series to which 

 these colors develop when the factor under consideration is present. In the case 

 of black and brown, factor P is assumed to be present. When p is present, black 

 and brown undergo a two-fold dilution. P is also considered present in the case 

 of eye-color. 



Yellow series redo to yellow2 in guinea-pigs; yellows to creams in Cavia 

 cutleri. 



Black series blacko to black2. 



Brown series browno to brown2- 



Eye color black, brown. 



