STUDIES IN HUMAN HEREDITY 



307 



The fraternities of charts, figures 24, 28, 30, and 35, are sufficiently 

 close to expectation to suggest a DR X DR cross. 



O-T-D 



n 



^i^ 



Fig. 33. 



Fig. 34. 



. Chart, figure 34, moreover again indicates that ambidexterity may 

 perhaps be specifically hereditary. In family history 35, "one grand- 

 child out of each family is left-handed." 



"^ 



0-H5i 



i 



Fig. 35. 



In fifty-three instances, among the total of one himdred, neither parent 

 is left-handed; these include fifteen instances where in addition neither 

 grandparent is left-handed; and ten where one or other grandparent is 

 left-handed. In thirty-eight instances no information is given concerning 

 grandparents; these include ten instances where either an imcle or aunt is 

 left-handed. 



The cases of total absence of left-handedness in the pedigree (for two 

 previous generations) of a left-handed individual are therefore very rare, 

 if indeed, they exist at all. Actual cases must be interpreted as spontane- 

 ous variations, which are probably just as liable to occur now as originally. 



