VIII] HEREDITY IN MAN 105 



occurrence of apparently continuous variation within 

 a discontinuous category is clearly shown. Of other 

 Mendel ian characters in man, colour-blindness, com- 

 plicated by its relation Avith sex, has already been 



Fig. 12. Bracbydactylous bands. (From Bateson, after Farabee.) 



mentioned and is further considered in Chapter ix. 

 Several cases are known in which an abnormality 

 behaves as a simple dominant, e.g. the condition of 



