THE AMERICAN NATURALIST [\ 



It is of interest to note that each form of variation ap- 

 pears in about one third of the off spring of the mothers 

 that bear the same variation. Where the mother does not 

 possess either type, the triangle appears in about one- 

 seventh of the offspring and the suppressed mamma in 

 one fourth. It is possible that a three-factor Mendelian 

 ratio would account for the results, but since the factors 

 are unknown it is scarcely worth while to present it. 



Two of the sows possessed both the triangle and the 

 suppressed mamma, and are not listed above. A close 

 agreement with the preceding table may be noted. 



The constancy of the per cent, of even pairs in the two 

 tables is undoubtedly worthy of notice. Neither boar pos- 

 sessed the triangle. Sows with the triangle produced 39 

 pigs with the triangle and 69 without. Sows without the 

 triangle produced 56 pigs with it and 349 without. The 

 character is apparently inherited as a distinct entity even 

 though it may be merely a function of an increased num- 

 ber of mammae. The sows without the triangle may be 

 divided on their breeding performance into two groups. 

 The first produced only offspring without triangles (124 

 pigs) while the second produced 56 pigs with triangles, 

 225 without. The proportions here look significant. In 

 the first group the ratio of those possessing triangles to 

 those without is about 1:2. In the second it is : N and 



