INHERITANCE OF ABNORMAL VENATION. 



19 



Fig. 52 shows graphically the results of the three sorts of matings : 

 normal X normal, normal X abnormal, and abnormal X abnormal. The 

 first should give one mode at zero abnormality and another at 25 per 

 cent abnormality on the assumption that normality is dominant in the 

 sense in which the term is now used in Mendelian literature. These 

 modes would represent the results of DD X DD and DR X DR, respec- 

 tively. They are present, but the curve runs all the way up to 65 per 

 cent abnormal. The second should give one mode at zero and another 

 at 50 per cent, representing the results of DDXRR and DRxRR, respec- 

 tively. The mode at 5 per cent is marked and might be explained as the 



5 15 25 35 45 55 65 75 



Percentage of abnormal individuals 

 Fig. 52. 



result of "incomplete dominance," a thing which is itself badly in need 

 of a Mendelian explanation. At 50 per cent there is a drop in the curve 

 where there should be a mode. There is a strong mode at 75 per cent, 

 where there should be none. This is true both when the male is the 

 normal parent and when the male is the abnormal one (see fig. 53). 

 Abnormal X abnormal should have but a single mode, 100 per cent (or 

 95 per cent as the figure is drawn), representing the result of RR X RR. 

 Such a mode is pronounced in the curve, being chiefly made up of the 

 families of the abnormal strain after generation vil, but the curve 

 reaches all the way to zero. 



These data are analyzed in tables 24 to 35, so that there is no need of 

 a further text description of them. They are taken from the early part 



