Sex-Determination in Sheep 



49 



in the case of the ewes that were mated 

 in October — the mothers of the 36 

 lambs born in March, 1900. 



"The weight records show that the 

 desired fluctuations of weight actually 

 occurred, and occurred — not only with 

 the twin-bearing ewes, but with the 

 single-bearing as well. 



"The fluctuations of weight seem to 

 have been somewhat greater with the 

 twin-bearing than the single-bearing 

 ewes — which is consistent with former 

 observations. 



" Forty-five .lambs were bom in the 

 spring of 1900; and of these, 16 

 or 36.6% were twins (eight pairs). 

 This was a smaller percentage than in 

 1899, although above the average for 

 the decade 1890-1899. Thirty-six of 

 these lambs were bom in March 1900 — 

 including all of the twins — 16 in number 

 or 44.4%: This percentage was less 

 than the a\"erage for March lambs during 

 the decade 1890-1899; but four of the 

 single lambs were from two-year old 

 mothers. If we deduct these we find 

 that 32 lambs were born in March 1900 

 from ewes three years of age or older — 16 

 single lambs and 16 twins (yielding the 

 maximum percentage hitherto attained ) . 



"On account of the small size of the 

 flock, a very slight change in the 

 absolute numbers would make a con- 

 siderable change in the percentages." 



The data, then, were not conclusive 

 as to whether the extra feeding given 

 the ewes in the fall of 1899 had caused 

 them to produce a larger percentage of 

 twins than ordinarv. But, continues. 

 Dr. Bell: 



"While the effect upon productive- 

 ness was not well marked it would be 

 premature to conclude that no effect at 

 all had been produced by the special 

 feeding; for no less than 72% of the 

 March-born lambs were females — a 

 circumstance quite unprecedented in the 

 history of the flock. 



"Of course the absolute numbers 

 were small — only 36 March-born lambs 

 in all ( 10 male and 26 female) — but the 

 preponderance of females was too mark- 

 ed to be entirely accidental, more 

 especially when we consider that the 

 average of the flock for ten years showed 

 males in excess. 



"Both among twins and single lambs 

 females predominated in March 1900. ' 

 Five pairs of male and female twins 

 were born in that month, and three 

 pairs in which both twins were female : — 

 Total eight pairs. No case occurred in 

 which both twins were male. Thus — 

 out of 16 twins, five were male and 11, 

 or 68.75% were female. Out of 20 

 single lambs five were male, and 15 or 

 75% female. 



" If climatic conditions were involved, 

 or general causes of any kind affecting 

 the whole Island of Cape Breton, it 

 seemed reasonable to suppose that an 

 unusual proportion of female lambs 

 would be found in the Island generally 

 in the spring of 1900. 



"My shepherd, Mr. John McKillop, 

 and Mr. Angus Mclnnis, of Beinn 

 Bhreagh, undertook an investigation of 

 this point; and, in May, 1900, they col- 

 lected statistics from the neighboring 

 farmers concerning the number of male 

 and female lambs born that Spring. 

 Thirty-two flocks were examined, con- 

 taining 371 lambs, — 202 of these were 

 males and 169 females. 



' ' In four flocks the males and females 

 were equally divided. In 14 flocks 

 males were in excess, and in 14 flocks 

 feinales. The summation of the whole 

 shows a majority of males (54.4%) : — 

 The large female percentage upon 

 Beinn Bhreagh was evidently, therefore, 

 a local matter. 



"In flock No. 23, belonging to Mr. 

 Farquhar Macrae, an unusual pro]3ortion 

 of male births occurred. Out of 

 26 lambs born upon his place no less 

 than 23 (or 88.5%) were males, and 

 only three (or 11.5%) were females. 



"This fact led to a special investiga- 

 iton of the treatment of his flock during 

 the preceding year (1899). It was found 

 that in the autumn of 1899 the ewes 

 were roaming at large upon an upland 

 pasture, unaccompanied by males, until 

 the middle of November, when the ram 

 was released and allowed to run with 

 the flock. The sheep received no care 

 until starvation drove them to the barn, 

 in the middle of January, 1900, after 

 which they were given a daily ration of 

 dry hay. In this case, then, mating 

 occurred late in November, or early in 



