638 



SCIENCE. 



[N. S. Vol. IX. No. 227. 



selective breeding the supernumerary mam- 

 mae could be developed from their rudi- 

 mentary condition into real functional nip- 

 ples yielding milk, and (2) whether in this 

 case the fertility of the ewes would be in- 

 creased. 



In the autumn of 1890 his shepherd, Mr. 

 John McKillop, made an examination of 

 the mammte of 890 sheep belonging to 

 farmers in the island of Cape Breton, Nova 

 Scotia. In 811 cases, or 91 %, the sheep 

 were normally nippled, having only two 

 nipples each. In 79 cases, or 9%, super- 

 numerary mammre were present in a more 

 or less developed condition. Some of these 

 sheep had three nipples, others four, a few 

 five, and one ewe had six nipples. In 52 

 cases, or 6 %, the extra nipples were so rudi- 

 mentary as to resemble pimples upon the 

 milk bag. In 27 cases, or 3%, the extra- 

 nipples, though much inferior in size to the 

 ordinary-nipples, seemed to be suflQciently 

 developed to be functional ; and most of 

 these sheep were purchased by Dr. Bell and 

 added to his flock. 



Dr. Bell presented statistics showing the 

 results often years selective breeding for 

 supernumerary mammte. The following 

 tables show the number and percentage of 

 lambs born each year having 2, 3, 4, 5 or 

 6 nipples, and the accompanying chart ex- 

 hibits the percentages in graphical form : 



Number of Lambs born each year from 1890 to 

 1899. 



Percentage of Lambs born each year from 1890 to 

 1899. 



Graphical Chart showing the percentage of Iambs 

 born each year from 1890 to 1899 having 2, 3, 4, 5 or 

 6 nipples (See Table II.). 



In the autumn of 1893 the flock was cut 

 down very severely, and only those ewes 

 were retained which had supernumerary 

 mammse in a functional condition. This 

 accounts for the small number of lambs 

 born in 1894. Since that time no ewe 

 lambs have been retained excepting those 

 having extra nipples large enough to yield 

 milk. 



No normally-nippled lambs (2-nippled) 

 have been born in the flock since 1894. 

 Three-nippled lambs are gradually disap- 



