PARKER AND BULLARD. — LITTERS AND NIPPLES IN SWINE. 



403 



shown us that the variations in the arrangements of the nipples are so 

 irregular that any classification of them must be more or less artificial. 

 Even in what we have called the regular plan, we are not disposed to 

 admit of so close a comparison of organs as to favor the institution of a 

 system of homologies for nipples such as Wentworth has suggested, 

 but we are more inclined to the opinion advanced by Bateson (1894, 

 p. 192) that the milk series as a whole is variously divided in difl:'erent 

 individuals or on the two sides of the same individual, and thus we 

 have attempted to avoid that unreality to which extreme forms of 

 morphological comparison lead. In discussing the arrangement of 

 the nipples in swine, we shall, therefore, not lay much stress on close 

 comparisons, but content ourselves with the division of the material 

 into the two chief classes already designated as regular and irregular. 

 In a few of the pigs that came under our observation nipples were 

 found so near the median line as to appear to be median in position. 

 Such nipples, however, can usually l^e shown to be really lateral in 

 position, and, as a matter of fact, all have been classed as belonging to 

 either the right side or the left. 



TABLE 3. 



The Pigs of 1000 litters, in all 5970, Classified According to the 

 NtTMBER OF Nipples in each. 



Xumbers of nipples in pigs. Gegenbaur (1S9S, p. 129) makes the 

 statement that swine possess from 8 to 10 nipples. Bateson (1894, 

 p. 190) records for young pigs 12 to 16, and Wentworth (1913, p. 268) 

 gives 8 to 16. In the thousand litters that we examined, as shown in 

 Table 3,. the smallest number of nipples present was 8, and the largest 

 18. The mode was 12, which was A'cry near the mean number for 

 the whole population, 12.2 — . 



