GUINEA-PIGS FROM ICA. 



27 



mon (or "red-eyed cinnamon/' plate 5, fig. 31) differs from silver agouti 

 in having brown hairs ticked with white instead of black hairs ticked 

 with white. It is one of the handsomest of guinea-pig varieties. Red- 

 eyed chocolate is indistinguishable from dark-eyed chocolate, except in 

 eye color. The red-eyed whites all look alike, though they may differ 

 considerably in factorial composition. Their production in this experi- 

 ment was a complete surprise to us and very puzzling until the sugges- 

 tion was made (I think by Mr. Wright) that an essential feature of 

 the red-eyed variation was the absence of yellow color from the fur. 

 It was then realized that a " yellow" animal with red eyes and " non- 

 yellow" fur must of necessity have white fur. This suggestion was 

 immediately put to the test by mating the red-eyed white c?576 with 

 3 dark-eyed cream females. They produced 12 young, of which 5 were 

 brown-eyed cream, 2 black-eyed cream, 3 red-eyed white, and 2 albino. 

 No young were produced which had coats of any other color than 

 yellow! Hence it is clear that red-eyed whites do not transmit the 

 extension factor. 1 



TABLE 17. Results of mating red-eyed white individuals with albinos. 



This same red-eyed white c?576 was also mated with 3 albino 

 females of race B, which carry the extension factor. Both parents, 

 it will be observed, were white, one having red eyes, the other pink eyes. 

 This mating produced 7 young, of which 3 were red-eyed with silver- 

 agouti-colored coats and 4 were albinos. The production of colored 

 young in this case shows that red-eyed white animals may transmit all 

 that is necessary for the production of a colored coat except the exten- 

 sion factor, which the albino parents supplied. 



The red-eyed white cf 576 was evidently heterozygous for the black 

 factor, since, when he was mated with brown-eyed cream females, he 

 produced both black-eyed and brown-eyed cream young. Another 



J As a further test of red-eyed whites, two other red-eyed white males (615 and 616) were mated 

 with several different red or yellow coated females. They produced 9 red or yellow young, 5 red- 

 eyed young, and 5 albino young, a result completely in accord with that given by d" 1 576. 



