62 INHERITANCE IN GUINEA-PIGS. 



series the ears and feet are quite black, often with intense black 

 blotches. Even in albinos, where the fur is nearly pure white, the ears 

 and feet may be black. In the pink-eyed sepias, on the other hand, 

 there is very little pigment anywhere in the skin. 



Brown fur goes with a uniform brown color of ears and feet very 

 different from the dull black of sepias of corresponding intensity of 

 fur color. Dilution in the skin accompanies dilution in the fur. 



The different skin colors are very conspicuous in animals with 

 spotted fur. In these it is easy to find places where the skin spots do 

 not correspond exactly to the fur spots. White fur may arise from 

 colored skin and yellow fur from black skin, but the reverse cases do 

 not seem to occur. 



EYE COLORS. 



The iris and retina usually contain black and brown pigment. 

 Where there is reduction of pigment in the iris, the pigment tends to 

 disappear first next to the pupil, leaving a dark outside ring. Decreas- 

 ing grades of retinal pigment are most easily recognized by the apparent 

 color of the pupil. In black eyes the pupil appears black. Occasion- 

 ally a red reflection can be obtained in strong light. In brown eyes a 

 dark-red reflection is easily obtained by holding the guinea-pig away 

 from the light. In the red eye the pupil looks red most of the time 

 and the inner ring of the iris often transmits red light. A pink eye 

 has a transparent iris and a pink reflection is visible through both iris 

 and pupil in all lights. 



The following summary shows the color terms to be used in this 

 paper, with their nearest equivalent on Ridgway's color charts (1912). 

 The numbers 15'i, etc., refer to the position in Ridgway's system. 

 For purposes of convenience in defining the color factors, white is 

 included as a member of each color series as well as in a class by itself. 

 In some cases white may be shown to represent extreme dilution of a 

 particular color; in other cases it stands in no relation to particular 

 colors. 



DEFINITION OF FUR COLORS BY RIDGWAY'S CHARTS. 



1 . Pigment absent because of factors not belonging to a dilution series. 



White. 



2. Pigment present, or absent only because of factors demonstrably belonging 



to a dilution series. 



a. Yellow group. 



Redo =15% ochraceous tawny. 



Yellow 3 = 16"6, redder than cinnamon buff, 17"6. 



Cream 6 = 19"/, cartridge buff. 



White. 



b. Dark group. 



(1) Black. 



Slaty black = dark neutral gray. 



Blue = neutral gray. 



White. 



