INHERITANCE OF ABNORMAL VENATION. 



15 



THE DATA CONCERNING INHERITANCE. 



Without reference to the grandparents, the data are summarized in 

 table 7: 



Table 7. 



In this work a fly is counted as abnormal if there is the slightest trace 

 of abnormality in either wing. These results leave no room for doubt 

 concerning the heritability of the tendency toward extra veins. 



Tables 8 to 19 show the relation between various ancestors and the 

 offspring. The coefficients of association found from these are given 

 below the respective tables. Although these coefficients are greater 

 than expectation on the basis of Pearson's Law of Ancestral Heredity, 

 they do not negative his conclusions. He was very careful to exclude 

 cases in which there is inbreeding or assortative mating. Both were 

 largely practiced in these experiments. These coefficients do show, how- 

 ever, that change of sex in the ancestry does not uniformly weaken in- 

 heritance. Thus, the average coefficient of association between father 

 and sons, and mothers and daughters (no change of sex) is 0.78 ; and 

 that between father and daughters, mothers and sons (one change of 



Table 8. 



SONS. 



Table 9. 



DAUGHTERS. 



C. A.=0.694. 



C. A. =0.736. 



Table 10. 



SONS. 



Table 11. 



DAUGHTERS. 



C. A. =0.819. 



C. A. =0.864 



