ii8 



HEREDITY AND EUGENICS 



(see also p. 122), which is evidentl}^ transmitted by 

 females to half their sons, as indicated in Fig. 23, 

 compiled from the data given. 



In another family, cited from Cunier, thirteen 

 cases of ichthyosis occurred in five generations, and 

 all the affected individuals were females. Hence the 



^ o 



n 

 in 



IT 



f 





)xn 



ri 



7 



Fig. 23. — Pedigree of Male Sex-Linked Ichthyosis. 



condition is in this family female sex-linked. The 

 character must, therefore, behave as a dominant in 

 the females of the latter family and as a recessive in 

 the females of the former family. 



An even more remarkable case of female sex-linked 

 inheritance is described by Cunier (1839), in which 



i'xD 



1^ 4^xn d 



i 



8 



Fig. 24. — Pedigree of Female Sex-Linked Colour-Blindness. 



colour-blindness is inherited from mother to daughter 

 alone through five generations (see Fig. 24) in a 

 Belgian family. This again appears to be because 

 the character is behaving as a dominant instead of 

 a recessive. 



The condition is transmitted from mother to 



