JOURNAL OF AGRICULTURAL RESEARCH 
DEPARTMENT OF AGRICULTURE 
Vol. V Washington, D. C., March 20, 1916 No. 25 
INHERITANCE OP FERTILITY IN SWINE 1 
[PRELIMINARY PAPER] 
By Edward N. Wentworth, Professor of Animal Breeding , and C. E. Aubel, Fellow 
in Animal Breeding , Kansas Agricultural Experiment Station 
INTRODUCTION 
Mendelian inheritance applies almost without exception to the trans¬ 
mission of qualitative characters. Quantitative traits, on the other hand, 
are susceptible only to a generalized treatment from this viewpoint, and 
few investigators have attacked the problem. Size inheritance in animals 
has been dealt with by Castle and Phillips (2) 2 , Goldschmidt (7), Mac- 
Dowell (10), Phillips (19, 20), and Punnett and Bailey (21), while Detlefsen 
(3) has treated the inheritance of certain skeletal characters. Pearl, 
(15) discovered an arbitrary division point of 30 eggs in the winter laying 
period of hens, for which inheritance apparently depends on two factors, 
one of which follows an ordinary Mendelian, and the other a sex-linked 
scheme. These determiners provide the nearest to units of inheritance 
that have yet been isolated in quantitative studies. 
Because of the fact that fecundity deviates only by discrete units, the 
litter size in swine provides peculiarly favorable material for studying 
quantitative inheritance. An analysis of this material has already been 
attempted from the biometric viewpoint. Rommel and Phillips (24) 
correlated the size of litters in which dams and daughters were farrowed 
and found a correlation coefficient of 0.0601 ±0.0086. They conclude 
from this result that there is an actual positive correlation between the 
size of litters of two successive generations, believing that size of litter is a 
character transmitted from mother to daughter. They recognize the small¬ 
ness of the coefficient, but believe the indications of inheritance are large 
enough to provide a basis for selection. In studying fertility inheritance 
Pearson and Lee (18) obtained practically similar coefficients with the 
human race and the thoroughbred horse. The range of correlation was 
0.0418 to 0.213; hence, they conclude that fertility is certainly and 
markedly inherited. 
1 Paper No. i from the Laboratory of Animal Technology, Kansas Experiment Station. 
2 Reference is made by number to “Literature cited,” p. 1159-1160, 
Journal of Agricultural Research, Vol. V, No. s% 
Dept, of Agriculture, Washington, D. C. Mar, so, 1916 
CO Kan,—1 
(1145) 
