>.590] SHORTER ARTICLES AND DISCUSSION 



TABLE II 

 Normal X Abnormal (Nn X nn). 



guished from the matings of homozygous dominants, NN, with 

 reeessives. In the former matings approximately 50 per cent, 

 of the children are expected to be abnormal. In the second 

 case only normal children are expected, who should all be hetero- 

 zygous for the abnormality. It is entirely possible in small 

 families that matings which should give part abnormal offspring 

 might give only normal children ; but all these matings are ex- 

 cluded, for no distinction can be made between them and the 

 more usual matings of abnormal with homozygous normal, also 

 giving only normal children. , 

 Having thus excluded part of the data, the modified ratio is 

 calculated as before, except that in this case it applies to a one- 

 to-one ratio, instead of a one-to-three. It ranges from 100 per 

 cent, in families with one child, to very nearly 50 per cent, m 

 families with fifteen children, and is calculated from the formula 



The agreement of observation with expectancy is very 



