PARKER AND BULLARD. 



LITTERS AND NIPPLES IN SWINE. 



401 



1 to 15, with a mean of 7.435 and a mode of 7, and litters of Duroc 

 Jersey pigs to vary from 1 to 19, with a mean of 9.337 and a mode 

 of 9, differences that 'may have been due to the fact that in many 

 instances the htters in our records Avere the first htters produced by 

 unselected females and may therefore have been smaller than those 

 of females taken for breeding purposes. 



Sexes. Of the 5970 pigs, 2946, or 49+ percent, were females and 

 3024, or 51 — percent, were males; that is, for every 100 females there 

 were 102.6+ males. This proportion agrees closely with that ob- 

 served by Wentworth (1912, p. 548) according to whom the males 

 exceed the females by about 2.02 percent. It is somewhat less than 

 the number given by Darwin (1895, p. 247), who stated, on the author- 

 ity of ]\Ir. Wier, that there are about 7 males to 6 females, that is, 

 the males exceed the females by about 16.7 percent. 



The distribution of the sexes in the litters of different sizes is given 



in Table 2. 



TABLE 2. 



Numbers and Proportions of Male and Female Pigs in 1000 litters op 



Different Sizes. 



An inspection of Table 2 will show that in no class does the percentage 

 of males rise above 62 nor fall below 43, but it is close to the general 

 average, 51 — percent, in all the classes of litters except the extremely 

 small one (1) and the large ones (10 to 15). In the former it is some- 

 what above the general average; in the latter it is below in litters of 

 10 to 12 pigs and above in litters of 13 to 15. These relations, however, 



