234 Journal of Agricultural Research voi.xxn.No.4 



From Table IV it can be clearly seen that the percentage of multiple 

 births is greater in the spring. If the births occurring from February 

 to June, inclusive, are combined it is found that 48.2 per cent are in 

 multiple births, while for the other months the percentage is 34.9. In 

 Shropshires a larger percentage of twins or multiple births occurs in 

 January, February, and March than later. This condition does not seem 

 to hold for the Dorsets. Therefore, this condition in the Shropshires is 

 not likely due to more green feed early in the mating season. The 

 causes of these significant differences in multiple births at different sea- 

 sons among sheep are yet to be discovered. 



SUMMARY 



(i) Multiple births increase with age up to 4 years. From this point 

 they remain fairly constant until 8 years. Beyond this age the numbers 

 are too small to draw conclusions. 



(2) The age of the ram has no influence on the percentage of multiple 

 births. 



(3) Among Shropshire sheep more multiple births occur early in the 

 lambing season than later. 



(4) Among Dorsets more multiple births occur in spring than in fall. 



LITERATURE CITED 

 (i) American Shropshire Registry Association. 



1912. AMERICAN SHROPSHIRE SHEEP RECORD. V. 25. 



(2) CARtYLE, W. L., and McConnell, T. F. 



1902. SOME OBSERVATIONS ON SHEEP BREEDING FROM THE EXPERIMENT STA- 

 TION FLOCK RECORDS. Wis. Agr. Exp. Sta. Bul. 95, 19 p. 



(3) Continental Dorset Club. 



1900-17. continental dorset club sheep record. v. i-16. 



(4) Heape, Walter. 



1899. abortion, barrenness, AND FERTILITY IN SHEEP. In JouT. Roy. Agr. 

 Soc. England, v. [60] (ser. 3, v. 10), no. 38, p. 217-248. 



(5) 



1900. note on the fertility of DIFFERENT BREEDS OF SHEEP, WITH RE- 

 MARKS ON THE PREVALENCE OF ABORTION AND BARRENNESS THEREIN, 



In Proc. Roy. Soc. [London], v. 65, 1899, p. 99-111. 



(6) Humphrey, George C, and Kleinheinz, Frank. 



1907. OBSERVATIONS ON SHEEP BREEDING FROM RECORDS OF THE UNIVER- 

 SITY FLOCK. In Wis. Agr. Exp. Sta. 24tli Ann. Rpt. 1906-07, p. 25-40, 



(7) Jones, Sarah V. H., and RousE, James E. 



1920. THE RELATION OF AGE OF DAM TO OBSERVED FECUNDITY IN DOMESTI- 

 CATED ANIMALS. I. MULTIPLE BIRTHS IN CATTLE AND SHEEP. /« 



Jour. Dairy Sci., v. 3, no. 4, p. 260-290. References, p. 288-290. 



