264 



THE AMERICAN NATURALIST [Vol. XLVII 



Relation of Increased Pairs to the Common Variations, 

 -A correlation was arranged between an increased num- 

 er of pairs and the two common asymmetrical varia- 



No.Sup^essed 





6Prs. 













24 



125 



mppressed nipples = 



r = .5089 ± .0447. 



While the correlation does not show a marked relation 

 between the number of triangles and the increased num- 

 ber of mammae, yet another method of plotting shows 

 that there is a very significant relation between them and 

 that the tendency to these variations may possibly be 

 only a function of a large number of mammae rather than 

 a definitely heritable unit. 



The increased percentage of animals with the two 

 types of variation among the animals with a larger num- 

 ber of mammae speaks for itself. 



This relation of the variations to the increased number 

 of pairs, in connection with the fact that the variations 

 appear most frequently in the pairs between the first, and 

 inguinal, furnishes additional basis for the statement 

 made earlier in the paper that the number of mamma? is 

 increased by modifications between the first and inguinal 

 pair. 



