HUMAN INHERITANCE 187 



the fingers are short have been descri})ed. One such 

 case — also a dominant — has been traced by JNIohr 

 and Wriedt through six generations which carries 

 the pedigree to the year 1764. Here the shortening 

 involves mainly the forefinger (fig. 68) . 



Fig. 68, — Four pairs of hands showing a shortened 

 condition of the fore-finger. {After Mohr and Wriedt.) 



Color-blindness is a sex-linked recessive character 

 in man. A color-blind man married to a normal 

 woman has only normal daughters and sons; all of 

 the daughters, however, transmit color-blindness to 

 half of their sons (fig. 69) . 



Color-blind women are rare, because they can 

 never arise unless a color-blind man marries a 

 w^oman who is color-blind, or else marries a normal 



