ALLEN. — THE HEREDITY OF COAT COLOR IN MICE. 77 



TABLE B. 



Only three of the ten litters (Nos. 4, 5, and 10) show the expected 

 equahty. Two of these were from the same pair, and as in the case 

 of the third litter, represent all the young obtained from the parents. 

 Evidently each of the two heterozygous parents was producing equal 

 numbers of D and of R gametes. In case of the pair producing the 

 first three litters, there is an excess of 33*- per cent of albinos, and 

 one entire litter of three contained no pigmented animals at all. The 

 heterozygous parent, if we may judge from the small number (13) of 

 young produced, furnished more albino than pigment gametes. The 

 opposite seems to have been the case with the pigmented parent of litters 

 7, 8, and 9, which aggregate 4 albinos, 8 pigmented offspring. Never- 

 theless the result is doubtless a chance one, since, although the first litter 

 shows a shortage of albinos, the second litter presents an excess. The 

 total result, 26 : 23, is a close approximation to the INfendelian expecta- 

 tion with the slight excess in favor of the albinos. Thus it appears that 

 although, in individual lots, there may be a considerable irregularity in the 

 proportions of the two sorts of gametes produced by the heterozygote, 

 yet in the long run the 1 : 1 ratio is practically realized. 



* Different individuals are distinguished by numerals, as stated on page 09. 



