38 



H. LUNDBOUG 



tional deaf-mutes (recessive homozygotes) and acquired deaf- 

 mutes (dominant homozygotes) 10 children were born, all hearing, 

 which is of course in harmony with Mendel'S law. The expectation 

 is 100 % normal children (dominant heterozygotes). 



In order further to examine this important problem I have made 

 new tabulations with the aid of Fays evidence. 



In the first place then I have brought together those families 

 in which all the children in each family to the number of 4 — 9 were 

 deaf (probably genotypically). There are 22 such families with 112 

 children in all. Mendels law requires that all the parents of these 

 children must have been deaf-mutes, which also is the case. 



The second grouping that I have made includes all such fam- 

 ilies (409 in number) of which all the children (2111) have posses- 

 sed normal hearing. Only families with at least 4 children have 

 been included. The following table gives an idea of the result. 



TABLE 1. 



Tabulation from Fay's evidence. 

 All the children hearing, 21J1 all told, from 409 families. 



In those cases where the Mendelian law is applicable it 

 requires that at least one of the parents in these marriages shall 

 be either hearing or affected with acquired deaf-mutism (in both 



