COLOR. 65 



Cd- Determines an intensity of yellow distinctly lower than does C, an intensity of dark pig- 

 mentation usually, but not always lower than does C, and an intensity of eye color 

 rarely distinguishable from that determined by C. More or less dominant over 

 C r and C a where distinguishable. (Wright, 1915.) 



Yellow series yellow2 to creamy. 



Black series blacko to sepiay. 



Brown series browno (?) to browny. 



Eye color black, brown. 



C r . Determines the complete absence of yellow, an intensity of dark pigmentation indis- 

 tinguishable from that determined by Cd and an intensity of eye color lower than 

 that determined by C or Cd- More or less dominant over C a where distinguish- 

 able. (Castle, 1914a; Wright, 1915.) 



Yellow series white. 



Black series blacko to sepias- 



Brown series browno (?) to brownj. 



Eye color red, brown-red. 



C a - Determines an absence of pigment, complete with yellow, not quite complete with 

 dark pigments of the fur and skin, but complete in the eyes. (Castle and Allen, 

 1903; Castle, 1905; Sollas, 1909; Detlefsen, 1914; Wright, 1915.) 



Yellow series white. 



Black series white, dark smudges on nose, ears, and feet. 



Brown series white, brown smudges on nose, ears, and feet. 



Eye color pink. 



DARK VS. YELLOW COLOR (2). 



Factors of this group affect skin and fur color, but not eye color. In 

 this group come the factors responsible for self yellows, tortoise-shells, 

 and brindles, on the one hand, and self blacks or browns on the other, 

 as contrasted with the ticked or agouti patterns of the wild rodents. 

 Where more than one factor is present which determines a yellow 

 pattern, combination effects are produced, such as in yellow-spotted 

 agoutis among guinea-pigs. The following factors are known in guinea- 

 pigs: 



E. A condition for more than a trace of dark pigmentation in the fur; determines dark pig- 

 mentation wherever yellow is not determined by other factors; dominant over e, 

 found in the wild species, all agoutis, blacks, browns, etc., but very rarely in self 

 yellows. 



e. Determines the presence of one of the yellow colors in all colored areas of the fur, aside 

 from a slight sootiness; responsible for the yellow in most self yellows, for the white 

 in red-eyed whites, etc. (Castle, 1905, 1907, 1907a; Sollas, 1909; Detlefsen, 1914.) 



A. Determines the presence of a yellow color in the light-bellied agouti pattern wherever 

 there is dark pigmentation in which the yellow group ticking may show; dominant 

 over A' and a, found in Cavia cutleri and light-belh'ed agouti guinea-pigs, includ- 

 ing the red-eyed silver agoutis, in which the agouti pattern is in white. 



A'. Determines the presence of yellow colors in a more restricted agouti pattern than does A, 

 a pattern usually characterized by a ticked belly not sharply distinct from the 

 sides in color; dominant over a, found in Cavia rufescens and in ticked-bellied agouti 

 hybrids which have rufescens ancestry. (Detlefsen, 1914.) 



a. Determines the absence of yellow group ticking in hairs of dark pigmentation; found in 

 blacks, browns, etc. (Castle, 1905, 1907, 1907a, 1913; Sollas, 1909; Detlefsen, 

 1914.) 



Sj/. An assemblage of unanalyzed factors which determine the presence of spots of a yellow 

 color, conditional on factors of group (1) ; found in black and yellow tortoise-shells, 

 black, yellow, and white tricolors, and in some red-eyed black and white bicolors; 

 probably responsible for an occasional self yellow, though never in the writer's 

 experience. 



