No. 557] INHERITANCE OF MAMM2E IN SWINE 271 



basis, we find a ratio of 1 : 1.7 and 1 : 2.06. There may be 

 significance in the difference between the two ratios, but 

 the writer is inclined to think there is not, for last year's 

 work gave 35 asymmetrical to 68 symmetrical pigs from 

 two asymmetrical parents, and 33 to 62 from one asym- 

 metrical parent. 



Another method of plotting these ratios shows that 

 differences may occur in connection with an increased 

 number of pairs. When the animals have ten pairs, only 

 four animals out of 199, or less than two per cent., show 

 the variations. When the animals have six pairs, the 

 number of animals having even pairs throughout are 

 about equal with the number having the variation, 127 

 and 135, respectively. When the animals have seven 

 pairs, the chances are about two to one that the animal 

 will have one or the other variation (33: 15). Placed on 

 a percentage basis the following table results, showmg 

 that asymmetry is closely related to an increased number 

 of pairs. 



Inheritance of Asymmetry.— The old boar possessed 

 his asymmetrical nipple on the left side, the young boar 

 on the right. The two boars were tabulated in their 

 matings to sows possessed of each kind of asymmetry. 



Old Boar (Extra Nipple on Left) 



