The progress of Genetics siuce the rediscovery of Meudel's papers. 407 



9 





mF 



Fig. 23. Pedigree of cougeuital cataract, after Nett leship, I.e., p. 40. The figures 

 in the circles show the total number of unaffected persons. 



9' 





Fig. 24. Pedigree of congenital cataract (after Nettleship). The descent is 

 peculiar in that the affection passed through one person described as unaffected. 



The investigation of human pedigrees is rendered difficult from 

 the fact that the normals and their offspring- are frequently omitted, 

 and also from the circumstance that different pathological conditions 



