384 



THE AMERICAN NATURALIST 



[Vol. XLIX 



suiting from such matings, we therefore leave out three fourths 

 of the families when we include only those showing the recessive 

 character in the offspring. In families of two children nine 

 sixteenths of the families are omitted. In general, the number of 

 families omitted in such a study is 3"/4", where n is the number 

 of children per family. In order to uvt the true Mendelian pro- 

 portions we must take account of these omitted families. The 

 accompanying table shows the most probable results in Professor 

 Ramaley's study had lie been able to include the proper propor- 

 tions of families in which left-handed children might have oc- 

 curred. 



Thus if Professor Ramaley had had at his disposal the full 

 number of families of this character there should have been 

 about 570 children in them, 116 of which were left-handed, or 

 20.37 per cent. 



This is somewhat lower than the theoretical 2.") per cent., and I 

 would suggest as a possible cause of this the fact that so many 

 children who are naturally left-handed are from early infancy 

 trained to be right-handed. Hence the number of left-handed 

 children reported is probably less than the true number of 

 recessives in these families. 



W. J. Spill man 



