GUINEA-PIGS FROM ICA. 



23 



CROSSES BETWEEN THE ICA RACE AND GUINEA-PIGS OF RACE C. 



An albino male guinea-pig (cf 54) of race C was mated with 5 golden 

 agouti females of the lea stock. It was hoped from this cross to learn 

 as promptly as possible the gametic composition of the lea race, since 

 race C contained a larger number of recessive Mendelian factors than 

 any other race in the laboratory. In this hope we were not disap- 

 pointed. Race C has already been described. It contains two different 

 recessive variations of the color factor, dilution and albinism, which are 

 allelomorphic with each other and with ordinary color, thus forming a 

 system of triple allelomorphs, C, C d , and C a , with dominance in the 

 order named (see Wright, 1915). It lacks agouti, black, and extension 

 factors. Visibly the animals of this race are either brown-eyed cream 

 or albino. Male 54 was an albino, bearing the color allelomorph C a , 

 which is recessive to the color allelomorph C d found in brown-eyed 

 cream individuals of race C. The mating between cf 54 and the 5 golden 

 agouti females of the lea race produced 13 young, 7 of which were 



Table 14. 



-Fi result of mating the albino &5J+ of race C with golden agouti 

 females of the lea race. 



golden agouti (like the mothers), 3 silver agouti, and 3 a dull black or 

 slate color, which will be called sepia. The silver agouti young were 

 like those produced by lea animals bred inter se. The sepia young 

 represented a new class not previously observed. In common with the 

 silver agoutis they had no yellow in their fur. The ticking and spotting 

 of silver agoutis was of white, as was also the spotting of the sepias, 

 which had no ticking. It seemed probable, therefore, as proved to be 

 the case, that the silver agouti and the sepia young differed from each 

 other only in the presence or absence of the agouti factor. But these 

 two classes of young taken together differ from golden agoutis in lacking 

 yellow pigmentation with which the golden agouti fur is ticked. They 

 also differ from golden agoutis in the intensity of the eye pigmentation, 

 which is very great in golden agoutis and blacks, but ordinarily shows 

 such reduction in silver agoutis and sepias that the eye by reflected light 

 has a deep red glow. It will be convenient to distinguish them as red- 



