INHERITANCE OF MINOR VARIATIONS IN INTENSITY. 93 



darkening. The darkening was about 1.0 among 40 animals C d C a 

 without South American blood, although with considerable BW blood 

 in most cases; among 23 animals C d C a or C r C a , with South American 

 blood, the average darkening is 2.0 twice as much. One case among 

 the latter was very striking. Male D238, a red-eyed sepia, C r C a , was 

 the palest sepia recorded. The tip of the hair was called sepia 8 ; the 

 base was nearly white. When 2 months old, most of the hair was still 

 of this pale color, but there were sharply contrasting areas which were 

 nearly black (sepia 2 ) on the nose, in spectacles around the eyes, in front 

 of the ears, on the feet, and in an asymmetrical patch on the back. At 

 the age of 4 months, most of the fur on the back was sepia 2 , although 

 the belly remained fairly light. In the lea and Arequipa stocks the 

 dark color always appears first on the nose, feet, and ears. These 

 are the darkest regions generally in all dilutes, a fact which recalls the 

 location of the dark smudges in sooty albino guinea-pigs and Hima- 

 layan rabbits. In adult animals with a large amount of South Ameri- 

 can blood, the darkening with age is so great that C dr C dr can seldom 

 be distinguished from C dr C a , although quite reliable predictions could 

 be made at birth as to the nature of the same animals. 



VARIATIONS OF EYE COLOR. 



The variations of eye color have not been studied as carefully as those 

 of yellow and sepia fur colors. In intense guinea-pigs (C ) the eye 

 ordinarily appears black (factors B and P of course assumed to be 

 present as throughout the discussion of dilution) ; in many cases, 

 however, it is possible in the proper light to obtain a red reflection 

 through the pupil. In dilute guinea-pigs C d C d , C d C r , or C d C a , the 

 eye also appears black ordinarily, but a red reflection seems to be 

 obtained more easily as a rule than in intense guinea-pigs. The differ- 

 ence is not great enough to be of value as a criterion. In guinea-pigs 

 which are C r C r or C r C a the pupil appears red in most lights and usually 

 the inner ring of the iris is transparent and also appears red. In very 

 few, if any, cases is the eye so dark that confusion with a dilute or 

 intense is possible. There is much variation in the amount of pigment 

 present. These variations are probably connected with differences in 

 stock and possibly imperfect dominance of C r over C a . No pigment 

 has been noted in the pink eyes of albinos. A red-eye can never be 

 confused with a pink-eyed type, unless, of course, factor p is present. 



SUMMARY. 



1 . First-order effects in the dilution of yellow are due to the presence 

 of various combinations of factors of the albino series of allelomorphs. 

 The red-eye and albino factors (C r and C a respectively), produce nearly 

 if not quite identical effects. In the case of black, first-order effects 

 may be due either to different combinations in the albino series or to 



