It 



INHERITANCE IN GUINEA-PIGS. 



utia then are 13, of the blacks 15, and of the albinos 17. The 

 DumericaJ relations ol the classes suggest a dihybrid Mendelian ratio 

 | g i, which is in entire agreement with existing knowledge of 

 odor inheritance in guinea-pigs (Castle, 1905; Sollas, 1909). C. cutleri 

 i- evidently homozygous for all Mendelian color factors, since it breeds 

 very true to color. Albino guinea-pigs from a black race are known 

 to possess two independent recessive modifications from this condition, 

 lacking both the agouti factor and the so-called color factor. As 



u-ds these factors, then, the wild race, cutleri, forms gametes AC, the 

 albino forms gametes ac, and the F x hybrids form gametes of the four 

 types \t '. Ac, aC\ and ac. From recombination of such gametes 

 Bhould arise in F 2 zygotes as in table 5. 



Table 5. 



1 AACC 



\:iCC 



2 A A' !c 

 4 AaCc 



■'>uti 



1 aaCC 



2 aaCc 



3 black 



1 AAcc 



2 Aacc 



3 albino 



1 aacc 



1 albino 



Th' ral kinds of albinos being similar in appearance, the expected 



result is 9 agouti. 3 black, 4 albino. The agreement with this expecta- 

 tion is fairly close (see table 6). 



Table 6. 



(b) CROSS 9 ALBINO (RACE C)Xt? CUTLERI. 



F t anini.il> from the cross between an albino of race C and a cutleri 

 male have produced 11 F 2 young, which fall into 7 color classes, dis- 

 regarding differences of intensity of pigmentation. These classes and 

 their numerical representation among the 44 young are as follows: 

 golden agouti, 10; black, 1: cinnamon, 8; black-eyed cream, 4; brown- 

 ing; chocolate, t; albino, 14. (Seeplate4.) The occurrence 

 of thee eral classes of 1", young is what previously existing knowl- 

 ; color inheritance among guinea-pigs would have led us to expect, 

 for it was known thai albinos of race C differed from agoutis in the same 

 two factors as the albinos of race B, viz, the agouti factor and the color 

 factor. In addition, the albinos of race C were known to differ from 

 lUtifl in two other factor-, -eon respectively in chocolate and yellow 

 The chocolate race may be considered to have arisen by a 

 recessive modification of the black factor B, and the yellow race by a 

 similar modification of the extension factor E. Accordingly this cross 



