No. 636] 6'f7.\7-;j /V(„s .i.\7> TC JIK L'( f IJ )>] s 47 



in characters in which environmental conditions are of 

 very much more importance than heredity. The rank 

 of the families has been calculated for the periods 1906- 

 1910, 1911-15 and 1916-19, making due corrections for 

 the effects of size of litter. As previously stated, high 

 correlations were found between the ranks in the first 

 two periods in most respects among the 23 inbred 

 families. Table XVII shows the ranks of the 5 surviv- 



TABLE XVII 



Eank of Families in Eesistance to Tuberculosis in 1919^ and Rank in 

 Other Characteristics during Two Periods, 1911-15 and 1916-19 



Mortality and size chara 

 litter and (in 1916-19) for 





il differenc 





he inf 



uence of b 













1 





k 





'I 



























2^ 2-3 2 4 1-1 1-1 1-1 I 1-1 2-1 3-1 2-3 2-3 

 4-2 5-5 5-5 3-3 4-3 4-3 j 4-5 \ 5-5 4-3 5-4 5-4 

 1-1 4-4 ! 1-3 4-4 3-4 3-4 | 3-3 ; 3-3 5-5 3-5 4-5 



ing families in the second and third period. The reality 

 of the differences among these families is evident. 

 Taking the following 6 characters— percentage born 

 alive, percentage of these raised, birth weight, gain to 

 33 days, frequency and size of litter — the correlation 

 between the ranks in the two periods is + .83. 



The positions of the families agree in the main with 

 those for the single year 1919. The position of family 

 35, however, is much better in most respects, a point 

 w^hich will be discussed later. 



The difficulty of classifying the families in the order of 

 general vigor is showTi by this table. Families 2, 13 and 

 39 present curious combinations of high vigor in certain 

 respects with weakness in others. It is true that there 

 is perfect correlation between the ranks in size of litter 

 and adult weight, but the order in which this places the 



