382 



SCIENCE 



[N. S. Vol. XXXVI. No. 925 



born on the place those that had the most 

 fully developed extra nipples, discarding the 

 others. 



The second plan seemed to be impracticable 

 on account of the small number of six-nippled 

 ewes that made their appearance. We had 

 perforce to keep all the six-nippled ewe lambs 

 that appeared in order to preserve the six- 

 nippled strain from the danger of extinction. 

 No selection by six-nippled ewes was possible; 

 and the bulk of the flock remained four- 

 nippled for years in spite of the continual use 

 of six-nippled rams. 



Females More Important than Males. — We 

 recognized the fact that we were breeding for 

 a female peculiarity; and that in this case 

 selection by females was probably more im- 

 portant than selection by males. 



In the hope of increasing the number of 

 lambs from which selection could be made we 

 determined to enlarge our flock; and, in the 

 autumn of 1903, we purchased several four- 

 nippled sheep and a large number of ordinary 

 two-nippled ewes, and used our six-nippled 

 rams with the whole flock. This plan in- 

 creased the number of lambs born in 1904 

 and reduced the percentage of six-nippled 

 sheep to 4.8 per cent. 



After one winter's experience it became ob- 

 vious that it was . inadvisable to have a large 

 flock on account of the increased expense and 

 the difficulty of preserving accurate records 

 with large numbers. 



In the autumn of 1904, therefore, we cut 

 down the flock to one half; retaining only 

 ewes having four or more functional nipples, 

 and in the spring of 1905 the percentage of 

 six-nippled lambs rose to 25.8 per cent. ; fol- 

 lowed by 23.6 per cent, in 1906, and 27.Y per 

 cent, in 1907. 



It was speedily realized that with a small 

 flock continuous inbreeding was inevitable; 

 and that it would be very advisable to intro- 

 duce new blood, as the flock was undoubtedly 

 deteriorating physically. The difficulty, how- 

 ever, was that no six-nippled sheep could be 

 found outside our own flock. We searched the 

 country far and wide, and offered fancy prices 

 without any success. 



Avoiding the Evils of Inbreeding. — In the 

 autumn of 1906 we tried the experiment of 

 loaning a six-nippled ram to a neighboring 

 farmer; and we offered him $10.00 apiece for 

 any six-nippled lambs produced, $15.00 for 

 seven-nippled and $20.00 for eight-nippled 

 lambs. As the result of this experiment we 

 were able, in 1907, to purchase two six-nippled 

 lambs. 



The experiment of loaning a ram was tried 

 again in the autumn of 1907, with the result 

 that in 1908 we were able to purchase four 

 six-nippled lambs, for which we paid the 

 farmer $40.00. This excited the interest of 

 other farmers, who now began to apply for 

 the loan of our rams under similar conditions 

 of payment for lambs. 



This plan of loaning rams turned out to be 

 a success; and by the autumn of 1909 it be- 

 came obvious that, by pursuing this plan, we 

 could rely upon surrounding farmers for a 

 continual supply of new six-nippled blood 

 without keeping a large flock oiirselves. 



Giving up the Four-nippled Breed. — In the 

 autumn of 1909, therefore, we cut down our 

 flock io six-nippled ewes alone, and distributed 

 our four-nippled and five-nippled ewes, as a 

 bonus, among the farmers who would use our 

 rams. 



In the spring of 1910, 50 per cent, of the 

 lambs bom on Beinn Bhreagh were six- 

 nippled; and we were also able to purchase a 

 number of six-nippled lambs from the farm- 

 ers. Very similar results were obtained in 

 1911. 



This spring (1912) 53.6 per cent, of our 

 lambs were six-nippled; and the records 

 handed in by the farmers who have used our 

 rams indicate that we shall probably be able 

 to purchase from fifteen to twenty six-nippled 

 lambs this year. 



The New Departure. — As it has now been 

 demonstrated that we can rely upon a con- 

 stant influx of new six-nippled blood from 

 outside, the time has come when we may be- 

 gin the selection of six-nippled sheep by fe- 

 males. We propose to cut down our small 

 flock still more this year, and keep only six- 



