24 INHERITANCE IN GUINEA-PIGS. 



eyed, it being understood that the red eye is invariably associated with 

 no-yellow in the coat. 



Four of the five lea mothers which were mated with of 54 had pro- 

 duced silver agouti (red-eyed) young by lea mates. Each of them 

 produced red-eyed young by c? 54 ; together they produced 5 dark-eyed 

 young (golden agouti) and 6 red-eyed (silver agouti or sepia). The 

 fifth lea mother (9509) had produced 11 golden agouti young when 

 mated with lea males known to be heterozygous for silver agouti. 

 (See table 12.) This is good evidence that she did not carry red-eye as 

 a recessive character and was accordingly homozygous for dark-eye. 

 By 6*54 she produced 2 golden agouti young. 



From these several facts it appears that dark-eyed lea animals 

 capable of producing red-eyed young when mated inter se, produce equal 

 numbers of dark-eyed and red-eyed young when mated to albinos, but 

 produce no albinos. This indicates that albinism is recessive both to 

 red-eye and dark-eye, an indication which the F 2 result confirms. It 

 will be shown further that the three conditions are mutually allelomor- 

 phic, so that a zygote may contain any two of the three, but not more. 

 Red-eye is in fact a fourth member of the albino series of allelomorphs, 

 which includes the following conditions in order of dominance : (1) ordi- 

 nary dark-eye and colored coat, such as is seen in Cavia cutleri and in 

 golden agouti animals of the lea race; (2) dark-eye with dilute coat, 

 seen in colored animals of race C; (3) red-eye and non-yellow coat; 

 (4) albino. (See Wright, 1915.) For convenience these allelomorphs 

 may be designated by C, C d , C r , and C a . The cross of lea females 

 with the albino cf 54 involves animals of the formulae CC or CC r mated 

 with an animal of the formula C a C a . The 7 golden agouti young are 

 expected to be of the formula CC a ; the 6 red-eyed young of the 

 formula C r C a . We may now compare the experimental with the 

 expected results of breeding such animals in various ways. 



THE F 2 GENERATION. 



One of the F x silver agouti males (c?517) was known from his pedi- 

 gree to be heterozygous in four characters, viz, red-eye vs. albinism, 

 agouti vs. non-agouti, black vs. brown, and extension vs. restriction. 

 His formula was accordingly C r C a AaBbEe, and we should expect him 

 to form gametes of 16 different sorts, all equally numerous. This 

 animal was mated with all three kinds of F : females, with the results 

 shown in table 15. The golden agouti females produced 25 young, 

 distributed among 10 classes very distinctly different in appearance. 

 These golden agouti females were known from pedigree to be hetero- 

 zygous for the same 4 factors as cf 517, but to contain a different allelo- 

 morph for albinism. Both he and they carried albinism as a recessive 

 character, but whereas he carried red-eye (C r ) as its dominant allelo- 

 morph, they carried dark-eye (the ordinary condition of the color 



