Feb. 17 ,1923 
Inheritance in Swine 
559 
for wild litter size this sow possessed must have been received through 
her sire. The average size of litters produced by the four Tamworth 
sows in this experiment was not up to the breed average, being only 
7.67 pigs. However, four of these six litters were gilt litters, produced 
before their dams had reached full maturity, which may partially account 
for their small average size. A direct influence of the sire on the size 
of the litter has been demonstrated only under the condition of his 
previous excessive sexual use ( 6 ), a condition which did not apply in this 
case. 
The data in regard to litter size in all these crosses are summarized in 
Table I. 
Table I. —Size of litters 
Description of dams. 
Total 
number 
of litters. 
Number 
of gUt 
litters. 
Extreme 
size of 
litters. 
Mean size 
of litters. 
Standard 
deviation of 
litter size. 
Pure-bred Tamworth. 
7 
5 
6 and 10 
7.86 
1. 46± . 26 
Fj wild X Tamworth. 
1 
1 
4 
Pure-bred Berkshire. 
2 
1 
7 and 10 
Pure-bred Duroc-Jersey. 
6 
2 
8 and 17 
IO. 67 
2. 62 ± .51 
Fj BerkshireXDuroc-Jersey.. 
17 
8 
3 and 12 
8. 88 
2. 88 ± .33 
F 2 Berkshire XDuroc-Jersey.. 
2 
2 
5 and 11 
INHERITANCE OF SET OF EARS 
Three of the breeds used in this investigation, the Berkshire, Tam¬ 
worth, and wild, have erect, pointed ears of fine or moderately fine 
texture, and, since all of the pigs produced by intercrossing showed a very 
similar sort of ear, these crosses furnish no evidence as to the factors for 
inheritance of the ear shape. The Duroc-Jersey breed, however, is char¬ 
acterized by a quite different shape of ear; hence the Berkshire X Duroc- 
Jersey cross throws some light upon this question and will be discussed 
in more detail. 
The Berkshire ear, in addition to being erect and pointed, is rather 
small and fine in proportion to the size and length of the body. It may 
droop somewhat with extreme age (9), but breaks forward at the head 
and not within the length of the ear. 
The Duroc-Jersey ear, while not a direct opposite, offers a good contrast 
in several respects. It is of medium size, not so pointed, and the outer 
third of it breaks over sharply and droops downward. There is consider¬ 
able variation in the amount of droop, but close inspection shows that 
these variations are rather closely correlated with variations in the general 
quality of the animal. Thus the large, extremely flabby ear, broken over 
more than breed ideals permit, is usually found on animals which show 
a general roughness and lack of quality. On the other hand, the ex¬ 
tremely fine, almost erect type of ear is closely associated with a lighter 
limbed, neater quality type of hog. It is not known at present whether 
this correlation is genetic linkage or due simply to the mechanics of 
growth. 
Both of the Duroc-Jersey sows and both of the Berkshire boars of the 
parental generation were typical of their breeds with respect to ear shape. 
The generation contained 29 pigs, and, with the exception of one boarr 
(PI. 1, C, D) and one sow in the first .litter, which was sired by a boar 
26550—23-6 
