406 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



TABLE 6. 



Numbers of Pigs from 1000 Litters Classified According to the Num- 

 bers OF Nipples on the Right and Left sides. 



differ by one, two, or three nipples. No cases were found where the 

 two sides differed by as much as four nipples. This form of compari- 

 son for the whole population as well as for the separate sexes is given 



in Table 7. 



TABLE 7. 



Percentages of Pigs in 1000 Litters in which the Nipples of the Right 

 AND Left Sides agree in Number, or differ by one, two, or three. 

 The Percentages are given for the Whole Population (5970 in- 

 dividuals), THE IMales (3024 Individuals), and the Females 

 (2946 Individuals). 



The correlation of the nipples of the two sides of the pigs is given in 

 Table 8. 



The coefficient of correlation of the right and left sets of nipples is 

 0.6063 ± .0055, a somewhat lower degree of correlation than was 

 found by Davenport and Bullard (1896, pp. 96) for the Miillerian 

 glands on the fore legs of swine. 



The correlation of the nipples of the two sides as exliibited by the 

 two sexes is shown in Table 9 for the males and in Table 10 for the 

 females. 



