Feb. 17, 1923 
Inheritance in Swine 
573 
The expectations on this basis are shown in Table VII. Aside from 
the superficial agreement between the expectations quoted and the 
actual numbers, several additional facts supporting the hypothesis may 
be mentioned. In both the blacks and nonblacks the reds constitute 
nine-sixteenths of the total number, and therefore red pigment depends 
upon the complementary action of two factors. From the results of the 
back-cross both factors must be present in the Duroc-Jersey. Also the 
black-and-whites constitute one-fourth of the black-carrying pigs, and 
therefore differ from the F/s by one important factor. Although the 
numbers are small, there is one bit of additional evidence in favor of the 
last conclusion. A black-and-white F 2 sow mated back to her sire pro¬ 
duced five pigs. One was all white, two were black-and-white, and two 
were black-and-red. One of the latter had a sandy belly. On the 
theory that the white of the dam differed by only one factor from the 
red of Fj the expectation was that half the pigs would show white, while 
upon a theory that white depends upon the absence of two factors, 
whether black was present or not, only one-fourth of them would have 
shown white. 
One other point in regard to color pattern remains to be discussed 
which is of particular interest from the standpoint of determining the 
color factors responsible for the large amount of black on the pure-bred 
Berkshire. That point is the size and extent of the black spots on the 
pigs showing black. In every one of the 47 black-and-red pigs the black 
was present in small spots and covered relatively little of the area of the 
pig's body (PI. 2, H). What little unevenness of distribution of the black 
spots occurred in this group of animals consisted in the spots being a little 
more frequent along the underline and on the posterior parts of the ani¬ 
mals. In some of the sandy-and-black animals the spots were similar 
to those on the black-and-reds; in others the spots were much larger and 
more numerous. In most of the black-red-and-whites, black-sandy-and- 
whites, and black-red-and-sandies the black was relatively abundant, 
often covering more than half of the animal. Every one of the black-and- 
whites (Fig. 19) possessed more black than the average of the black-and- 
reds, and the average amount of black on the black-and-whites exceeded 
that of any other group, being probably a little more than half the body 
surface. A large amount of variation was shown among the black-and- 
whites, for they varied from as little as about one-tenth black up to almost 
the Berkshire amount. Since no pig with absolutely perfect Berkshire 
markings was produced (PI. 2, J) the evidence indicates that the Berkshire 
pattern is composed of the fundamental factor for black spotting, a factor 
for restricting or diluting the sandy pigment, and at least two or three, 
probably more, independent factors which operate to extend the black. 
The small amount of black in the F A generation, both of the Berkshire by 
Tamworth cross and of the Berkshire by Duroc-Jersey cross, and the fact 
that all red-and-blacks of the F 2 generation carry a similarly small amount 
of black are strong evidence either that there is a factor which strongly 
restricts black and is linked with red, or that, as Wright suggests (24), 
the competition between the two processes of pigment formation precludes 
the possibility of a pig possessing both an intense red and a large amount 
of black. The large average amount of black and the wide variation in 
the pattern of the black-and-white pigs indicate that the extent of the 
black spotting is influenced by many extension and restriction factors* 
even when free from the influence of the red. 
