COLOR. 63 



b. Dark group — Continued. 



(2) Black. 



Sepia 3 = 16"'w, warmer and darker than clove brown, 17"' m. 

 Sepia 6 = 16"'Z, warmer and lighter than clove brown, 17'" m. 

 Sepia 9 = 17"'% hair brown, slightly purer, however. 

 Sepia l2 = 17""6, light drab, somewhat purer. 

 Sepia 1 5 = 17""/, pale drab gray, somewhat purer. 

 White. 



(3) Brown =15" m, bister, 15"m, but somewhat warmer and duller. 

 Brown 3 = 15"% between army brown, 13"% and buffy brown, \T"i. 

 Brown 6 = 17"'fe, somewhat duller than avellaneous, 17'"6. 

 Brown 9 = 17""/? 



White. 



DEFINITIONS OF EYE COLORS. 



(1) Black: black iris and pupil. 



Dark red : black iris, dark-red pupil in favorable lights. 

 Red : partially transparent iris, red pupil in most lights. 

 Pink : transparent iris, pink reflection through both iris and pupil. 



(2) Brown: brown iris, dark-red pupil. 



Brown-red: partially transparent brown iris, red pupil. 

 Pink: as above. 



HEREDITY OF FUR AND EYE COLOR. 



COLOR FACTORS OF GUINEA-PIGS. 



Considerable work has been done on the inheritance of color varia- 

 tions in guinea-pigs. The numerous colors which have been listed and 

 several patterns in which these colors may be arranged have been found 

 to be due in the main to relatively few hereditary factors. Some of 

 these factors determine effects which are very easily defined. Thus, 

 any guinea-pig which is homozygous for factor C a is an albino with pink 

 eyes and white fur, regardless of the presence of any combination of 

 other known factors. On the other hand, certain factors determine 

 nothing except in combination with other factors. Factor E may be 

 present in guinea-pigs of any known color variety whatever. It can 

 only be said that its presence is a necessary condition for the develop- 

 ment of more than a trace of dark pigmentation in the fur. The color 

 which results from a given combination of factors can be made clear 

 most easily by classifying the factors into a series of groups. The 

 following classification is based upon the factors in the rodents which 

 have been most studied, viz, guinea-pigs, mice, rats, and rabbits. 



CLASSIFICATION OF COLOR FACTORS. 



1. Factors which affect the distribution and intensity of color largely irre- 



spective of the kind of color. 



A. Factors which govern the distribution of color as opposed to no color 



(white) in patterns in the fur, in individual hairs, and in the eyes. 



B. Factors which govern the intensity of general color development 



within colored areas of fur and eyes. 



2. Factors which govern the differentiation between yellow and dark colors 



in colored areas of the fur. 



3. Factors which determine the kind of dark color in the areas with dark 



pigmentation in fur and eyes, without influence on yellow areas. 



