No. 557] INHERITANCE OF MAMM2E IN SWINE 275 



Eighty-three asymmetrical sows show only one indi- 

 vidual whose asymmetry is due to the presence of a rudi- 

 mentary. One sow has a rudimentary, but is asymmet- 

 rical from a functional ' ' triangle," and one symmetrical 

 sow shows a rudimentary in one of her pairs. 



Summarized this shows that only 1.123 per cent, of the 

 asymmetrical males have their asymmetry caused by 

 rudimentaries, and only 1.204 per cent, of the females. 

 From this evidence it would seem that rudimentaries do 

 not represent a step in the variation of the mammary 

 linear series, but from the standpoint of heredity should 

 be treated the same as normal teats, the lack of develop- 

 ment being probably due to fluctuating somatic causes. 



It is interesting to compare the variability of the nip- 

 ples of the male, which are rudimentary throughout life, 

 with the teats of the female, which are potentially func- 

 tional. The coefficient of variability for the boar pigs is 

 .1009 ± .003 and for the sow pigs it is .0943 ± .0028. The 

 probable error permits a minimum separation of the two 

 coefficients of only .0008, so that the difference between 

 the two is probably not significant. In the litters of 1911, 

 already referred to, the boar pigs were slightly more 

 stable than the sows, which would further argue against 

 a qualitatively constant significant difference. 



The Rudimentaries to the Rear of the Inguinal Pair — 

 In the previous discussion no account has been taken of a 

 pair of rudimentaries which occur on the lower forward 

 part of the scrotum of the male, and well to the rear on 

 the inner thighs of the female. The pair is entirely dis- 

 tinct from the others, and readily recognizable from its 

 location and also from the fact that so far as the writer 

 has observed it is always rudimentary. It seems prob- 

 able that it lacks almost entirely the backing of mammary 

 tissue found in the other mammae. The writer has already 

 described the inheritance of the character in another 

 Paper, so will simply summarize the results. The pair 

 behave as a Mendelian unit character in heredity, domi- 

 nant in males but recessive in females. That is, it is 



