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 d"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 d"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 



x 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 c? 576. 



