26 s 



THE AMERICAN NATURALIST [Vol. XLVII 



approximately equal to the coefficient or else far larger, 

 so that no emphasis can be placed on the result. In 

 arranging them according to per cent, of offspring bear- 

 ing the same variation the following is obtained: 



Grand-dams without suppressed nipple 23.00 



No difference shows between the two clas 

 possible that the presence of the variation 

 tends to even things up. 



In the case of the triangle, the grand-dams without the 

 variation have a higher per cent, of offspring possessing 

 it than do the dams, but where the triangle is present in 

 the dams and grand-dams the younger generation seems 

 to have the greater power of transmission. Since the old 

 boar previously mentioned is the sire of the dams, and 

 the young boar the sire of the 1912 pigs, there has been no 

 point of entrance for the triangle somatically. The per- 

 centages show some sort of segregation of a recessive 

 character, but further matings are necessary to clarify 

 the matter. 



Variation in Number of Mammce.— There is quite a 

 wide range in the number of teats that may be present. 

 The smallest number found in these litters is nine, while 

 in the litters of last year, elsewhere reported, one pig ap- 

 peared with only eight. The highest number recorded 

 on one animal was sixteen, these including a pair of rudi- 

 mentaries to the rear of the inguinal pair. Of the mam- 

 mae on the mammary lines of the abdomen fourteen is 

 highest number. 



The relative frequency of occurrence of these different 



