16 



INHERITANCE IN GUINEA-PIGS. 



(c) CROSS 9 BROWN-EYED CREAM (RACE C) X <f CUTLER1. 



The F! animals produced by crossing brown-eyed cream females of 

 race C with cutleri males themselves produced 132 F 2 young, distributed 

 among the same 7 classes as the albino cross had produced (table 8). 



TABLE 8. 



Except in regard to albinos, the result expected from this cross is the 

 same as that expected from crossing albinos of race C. Accordingly 

 the albinos may be for the moment disregarded. The expectation as 

 regards the colored classes of young may then be stated as shown in the 

 column of " observed" results. 



The occurrence of 16 albinos in this F 2 generation shows that certain 

 of the F! pairs were heterozygous for this character, which they obvi- 

 ously derived from the brown-eyed cream parent, not from the cutleri 

 parent; for the brown-eyed cream animals of race C were known in 

 many cases to be capable of producing albinos, whereas the cutleri stock 

 bred true. Accordingly such pairs of F! animals from this cross as pro- 

 duced albino young should be tabulated with the hybrids produced by 

 crossing albinos of race C with cutleri males. If this is done there 

 remain 68 instead of 116 F 2 young to be considered. Among these are 

 3 albinos which it is impossible to transfer to table 7, because it is not 

 known what colored individuals were born in the same litters with them. 

 They were born in a pen containing 2 females which had young simul- 

 taneously, one of which was known to produce albino young, though 

 the other did not. Omitting the 3 albinos, there remain 65 colored 

 young, distributed as shown in table 9. 



TABLE 9. 



(d) RESULTS FROM (b) AND (c) COMBINED. 



Since the expectation is the same as regards the relative proportions 

 of the several colored classes in all crosses of race C females (whether 

 albino or colored) with cutleri males, we may legitimately combine all 



