No. 611] FERTILITY IN SOUTHDOWN SHEEP 681 



on heredity, the most important factors being the vigor 

 of ewe, the feeding of ewe, the age of ewe, the season and 

 the region. 



5. Apparently no relation exists between high fertility 

 and additional mammsB. 



6. In pedigrees started from single births, the birth 

 rank of the sire does not affect the birth rank of the prog- 

 eny; in pedigrees started from twin births, the effect of 

 high birth rank of the sire is only slightly significant 

 (more than three times the probable error). 



7. The effect of birth rank of ewe on the birth rank of 

 progeny is the same as that of the sire except in the case 

 of pedigrees started from twin births when it is slightly 

 greater. 



8. No evidence for a sex linkage of fecundity factors 

 occurs in the pedigrees tabulated, as shown by a com- 

 parison of the relative influence of progeny of the mater^ 

 nal grandam and the maternal grandsire. 



9. Evidence from Shropshire triplet pedigrees suggests 

 that triplets are genetically different from twins and 

 singles, which two are probably genetically alike. 



LITERATUEE CITED 

 Ainsworth-Davis, J. E., and Turner, D. 



1913. Fecundity of Sheep. In V Cong. Internat. Agr. Gand., Sec. 3, 

 question 4, p. 5. 

 Bell, Alexander Graham. 



1904. The Multinippled Sheep of Beinn Breagh. In Science, N. S., 

 Vol. 19, p. 767. 



CarlTle, W. L.. and McConnell, T. F. 



1912. Some Observations on Sheep Breeding from the Experimenta- 

 tion Flock Eecords. In Wisconsin Sta. Bui., 95, p. 19. 



Evvard, J. M. 



1913. Unpublished Data. 

 Heape, Walter. 



1899. Abortion, Barrenness and Fertility in Sheep. In Journal of 

 Royal Agr. Soc. England, 3d series, Vol. 10, pp. 234-248. 

 Humphrey, Geo. C, and Kleinheinz, Frank. 



1907. Observations on Sheep Breeding from Eecords of the University 

 Flock. In 24th Annual Report, Agr. Exp. Sta., University of 



