Feb. 17. 1923 
Inheritance in Swine 
571 
large litter nor separately in two other litters. There is probably nothing 
more mysterious about this case of “reversion” than there is about any 
other case of the complementary action of factors. The indicated few¬ 
ness of the factors affords hope for their future analysis. 
The first step in investigating the nature of the genetic differences 
between the red, sandy, and white pigments was to discover whether 
the presence of the black pigment affects the other three in any way. 
To do this, Table III was rearranged with the black carriers separated 
from the nonblacks. The result, together with the numbers to be 
expected on the theory that the blacks and nonblacks of each combina¬ 
tion of red, sandy, or white should give a 3 to 1 ratio, is shown in 
Table VI. 
Table VI.— The relation of black pigment to the distribution of red , sandy, and white. 
Color. 
Number 
which also 
show black. 
Number 
not show¬ 
ing black. 
Expected 
blacks. 
Expected 
nonblacks. 
Red. 
47 
14 
45-75 
15-25 
Red-and-sandy.. 
10 
3 
9 - 75 
3 - 25 
Red-and-white. 
10 
3 
9-75 
3- 25 
Sandy... 
11 
7 
* 3-5 
4-5 
Sandy-and-white. 
6 
7 
9-75 
3 - 25 
White. 
27 
3 
22.5 
7-5 
It will be seen at a glance that the proportion of animals which had 
any red on them but lacked black color to those of the same color with 
the addition of black was almost exactly 1 to 3, or, in other words, the 
inheritance of the black is independent of the inheritance of the red 
(disregarding the pattern of the color). The numbers of the black 
and nonblack sandy and sandy-and-white pigs were too small for cer¬ 
tainty, but they were far enough from the expectations to indicate a 
disturbing influence at work here. The number of whites was large 
enough and the actual ratio was aberrant enough to permit the positive 
assertion that the black-and-white pigs were not simply white pigs to 
which black had been added. There was also a difference in the appear¬ 
ance of the white hairs in self whites and in black-and-whites. No 
microscopical examinations were made, but the white of the black-and- 
white pigs was a more lustrous white at birth and tended much more 
to remain quite white all through life than that of the pigs bom self 
white. One of the latter developed a sandy tinge at maturity, and two 
pigs bom a very light sandy became quite white at maturity, indicating 
that the very dilute sandies approach very closely to the whites. The 
whites are certainly not albinos, for their eyes are always pigmented, 
and one of them had large patches of black pigment in her skin, although 
the hair growing out of those patches was quite white. 
The second step in investigating the nature of the genetic differences 
between the red, sandy, and white pigments was to rearrange Table IV, 
classifying the bicolor reds according to the darker pigment which they 
showed. That the greater intensity of red represents the true pigment 
condition if there were no interference from bicolor factors is indicated 
by the fact that it was always the greater intensity of red which appeared 
as spots upon the lesser intensity. This classification is given in Table 
VII. 
