AT.LEN. THE HEREDITY OF COAT COLOR IN MICE. 



TABLE A. 



tained an excess of pigmented individuals, and the excess is very slight, 

 0.25 in one case, and 1 in the other, an average of less than 1. The 

 entire excess of albimre being 7.75, the average excess is thus less than 

 one for each of the nine litters which show deviation from tlie Mendeliau 

 ratio. To be sure, the totals are not large, and the results may be purely 

 a matter of chance in the union of the gametes, yet the deviation may have 

 some significance which has not yet been fully appreciated. Thinking 

 that the production of an excess of albinos might be an individual pecu- 

 liarity of the parents, wherein an unequal number of pigment and non- 

 pigment gametes were given off, two of the heterozygous, Fj. males were 

 bred to albinos ; but these produced an excess of pigmented individuals, 

 there being in 17 litters 35 pigmented mice as against 23 albinos, where 

 — according to formula (1) — equality is expected. Curiously, the ex- 

 cess of albinos in the litters from cross-breds nearly offsets the shortage 

 in the lots obtained by back crossing with the albino parent. Thus in 

 the first case, out of a total of GO young, we expect 17 to be albinos, and 

 obtain 25. In the second case, 29 albinos are expected, and only 23 

 occurred. In all, therefore, 48 albinos were produced, where 4G are 



