52 



The Journal of Heredity 



much heavier on the avera<;;e than the 

 single-bearing ewes, but their weight 

 increased much more rajiidly for some 

 time after mating. 



SIGNIFICANT DECLINE. 



"We then calculated the aggregate 

 and average weekly weights of the 

 mothers of the 10 male lambs bom in 

 March, 1900, and of the mothers of the 

 26 female lambs born at the same time. 



"The male-bearing ewes, on the 

 average, weighed more than the female- 

 bearing at the time of mating, but lost 

 weight so much more rapidly after 

 mating, that in a few weeks the female- 

 bearing ewes were the heavier, a super- 

 iority afterwards retained throughout 

 the whole period of gestation. 



"The male-Vjcaring ewes were losing 

 in weight at the time of mating and 

 immediately afterwards, in a much 

 more marked degree than in the case of 

 the female-bearing ewes. 



"In the above calculations, the 

 weights of the five ewes who had both 

 male and female twins were included 

 once among the mothers of male lambs, 

 and once among the mothers of female 

 lambs. 



"A second computation was made, 

 from which these ewes were excluded, 

 so that it referred to ewes who had male 

 lambs exclusively, or female lambs 

 exclusively. It was found that the 

 mothers of males averaged less in weight 

 than the mothers of females; but the 

 characteristic changes of weight at or 

 about the time of mating are the same 

 as noted Vjcfore. The mothers of males 

 were losing in weight at the time of 

 mating ; whereas the mothers of females 

 retained their weight." 



On the basis of these figures. Dr. Bell 

 placed on record the following "Con- 

 clusion": 



" It is to be regretted llial the number 

 of cases examined in this jjajjcr is too 

 small to enable us to feel full confidence 

 in the accuracy of the results, but the 

 indications seem to point to the con- 

 clusion that variations of weight oc- 

 curring at or aljout the time of mating 

 may have great significance. 



"They refiect changes in the con- 

 dition of nutrition of the mother, at 



a critical i)eriod in the formation of the 

 unborn young; and suggest the possi- 

 bility of affecting the fertility of sheep, 

 and controling the sex of their offspring, 

 by suitable feeding for a short period of 

 time before and after the time of mating." 



INVESTIGATION RESUMED. 



Such was the status of the investi- 

 gation at the close of Dr. Bell's first ten 

 years of work with this breed of sheep. 

 He did not publish the j^aper abstracted 

 above, however, but merely placed it 

 on record among his own papers, making 

 a note that "Some of the conclusions 

 suggested were of so startling a char- 

 acter that it was thought better to 

 await the collection of larger statistics 

 before publishing the results." 



In 1901 he returned to this subject, 

 and on October 17 dictated a memo- 

 randum of the above results, continued 

 by the following comment: 



' 'These resiilts have afforded some 

 ground for the belief that there is a 

 sen.siblc difference in the weight changes 

 of the mothers of male and female lambs 

 about the latter part of October or the 

 early ]jart of November; and that loss 

 of wxMght is associated with the pro- 

 duction of male lambs; increase of 

 weight at this time associated with the 

 production of female lambs. 



"I have ahvays felt, however, that 

 the absolute numbers involved were too 

 small to gi\'e certainty to the averages 

 and I still feel that we must wait for 

 more numerous observations before 

 announcing definite conclusions. 



"It has occurred to me that by 

 adding the lambs born 1900 and 1901 to 

 those born during the decade 1890-1899, 

 the absolute numbers involved would be 

 increased, and the averages resulting 

 therefore more certain." 



The data made available in 1901 re- 

 sulted from the l)irth of thirty-two 

 lambs at Beinn Bhreagh, 14 male, and 

 18 female. The mothers of the 14 

 males weighed 1293 lbs. at the end of 

 September, 1900; 1267 lbs. end of 

 October; 1238 lbs. end of November; 

 1221 Ihs,. end of December; average 

 weights 92.4 lbs. Sei)tember; 90.7 lbs, 

 Oct()l)er; 88.4 ll)s. Xowmber; 87.2 lbs. 

 December. 



