114 Hagedoorn. 



two genes, just as yellow colour and waltzing, in the other series, 

 becomes much greater. As, however, the inheritance of albinism in this 

 case could not be tested, the albino young dying young, we refrain 

 from naming two more genes. 



One pair of paleagoutj F2 animals was mated and produced 5 pale 

 young. A pale F2 male was mated .to an agouti sister and gave 

 3 agouti and 3 pale young. All this shows the pale colour to result 

 frdip. absence of another gene from the wildcaught paleagouti female. 



Albinism. 



We next turn to albinism. The albino female proved to be very 

 small, even when adult. She was very fertile and produced three litters 

 of Fl young from the Sumatra male. In all we obtained 21 young, all 

 agouti, but with white bellies. The albino wild female must have 

 canied factor B, and have been homozygous for it, BB. We will later 

 return to this fact. Before any F2 animals were born, the white mother 

 was bred to a son from her first litter. From this mating she gave 2 

 agoutis and 4 albinos. The bellycolour f)f the agoutis has not been 

 registered. 



In all 22 F2 animals were produced from matings of Fi rats inter se. 

 They comprised 12 agoutis, 10 albinos, of which two waltzers 

 (Exp: 12-6 : 9-8). This is a peculiar ratio to find in such an F«. The 

 albinos are far to numerous to make it probable, that the original 

 albino female differed from her normallycoloured mate in only one gene. 

 The ratio 9, which would be obtained if the female lacked two separate 

 genes, the aliseuce of each of which would give albinism, fits much 

 better. We will see from later work with albinism in this family that 

 this is the correct explanation. 



r)ne young pair of agouti F% rats bred and produced 15 agouti 

 to 4 albinos, which looks like a 3 : 1 ratio. At this point an epidemic 

 made us lose so many of our rats, that we gave up trying to breed 

 them, and killed almost everything, with the exception of a likelylooking 

 pair of albinos, brother and sister, F2 animals. These did not breed 

 for some time but evidently they recovered, and then produced three 

 litters. To our suiprise all these young were agouti like wild rats, 

 14 in all. 



This fact beai's out the existance of two factors. The only 

 explanation which fits the facts is, that each of these two rats was 

 homozygous for a gene whose presence or absence makes the difference 



