Feb 17., 1923 
Inheritance in Swine 
581 
with and males without rudimentaries. The other five matings show 
altogether only 2 males without the rudimentaries and 32 with the 
character. The data do not furnish critical evidence as to whether 
there are different genotypes among the females or whether there is 
merely a quite abnormal distribution. The numbers, of course, are not 
large, but they approximate so closely a simple 3 to 1 ratio for the 
males and a simple 1 to 1 ratio for the females from the first type of 
mating that they suggest strongly that the true explanation must be 
simple. 
All the animals of the first and third types were entirely Berkshire 
and Duroc-Jersey in their ancestry. Three matings of the second type 
were entirely Tamworth and wild in their ancestry, and the fourth mating 
of this type was between a pure-bred Berkshire boar and a pure-bred Tam¬ 
worth sow. The only mating of the fourth type was between a pure-bred 
Berkshire sow and the wild boar. Hence it appears at least possible that 
there may exist differences between the breeds in respect to the factor 
complex which cause this pair of mammae to be present. Thus, the 
matings of the second and fourth types, which produce the small per¬ 
centages of progeny with rudimentary mammae (or none at all) include 
all the matings in which either Tamworth or wild blood is involved. 
Likewise all the matings in the first and third types involve only Duroc- 
Jersey and Berkshire blood, most of them being matings between F 1 
individuals. It is worthy of note that the original theory of sex-limited 
inheritance of this character was based almost entirely upon data obtained 
from high-grade or pure-bred Duroc-Jersey animals ( 21 ). 
It is not possible from these data to show clearly which of the expres¬ 
sions of the character is the dominant one. From the evidence of the 
matings of the first and second types it would seem that the possession 
of the rudimentaries was the dominant form of the character, since 
parents lacking them produce only offspring like themselves while 
parents possessing them produce both kinds of offspring. However, 
such an hypothesis entirely fails to explain the great preponderance of 
progeny without the character in the matings of the third and fourth 
types. 
Since the numbers of animals in this study are so much smaller than in 
those previously reported by the senior author, and since there was so 
much confusion incidental to the entering into the military service of 
three of the four men connected with the records on this work, it is 
believed best not to consider the evidence critical until further data are 
secured which either support or discount the present records. 
LITERATURE CITED 
(1) Babcock, Ernest Brown, and Clausen, Roy Elwood. 
1918. genetics in relation to agriculture, xx, 675 p., 239 fig., 4 col. pi. 
New York and London. Literature cited, p. 622-647. 
(2) Castle, W. E. * 
1916. genetics and eugenics, a textbook for students of biology and 
a REFERENCE BOOK FOR ANIMAL AND PLANT BREEDERS, vi, 353 p. f 
135 fig. in text and on pi. (2 col.). Cambridge, Mass., and London. 
Bibliography, p. 322-346. 
(3) Detlefsen, J. A., and Carmichael, W. J. 
1921. inheritance of syndactylism, black AND DILUTION IN swine. In 
Jour. Agr. Research, v. 20, no. 8, p. 595-604, pi. 70. Literature cited, 
p. 604. 
