404 



W. Batesoll. 



freed from the peculiarity, just as the hornless rams in F., are freed 

 from the horned character. In the human cases the evidence is still 



(^ 



c^ 



f ^ 



V^^ n 



ji 



^H ^04^ ^^^ 



5^ (TJTT^ 



Fig. 18. Pedigree of a family contaiuiug coloiir-bliud members observed by Dr. Ri- 

 vers, among tbe Todas. an Indian Hill-tribe, ilhistrating the "Knight's Move" 



descent of that condition. 



very imperfect (see Bateson (7)j and all that can be said is that 

 the general course of the descent is in rough agreement with such 

 scheme. 



It would follow in such a case as colour-blindness, where the 

 unaffected females can transmit, that a colour-blind female must be 

 pure to the colour-blind character. Therefore all her sons should 

 exhibit it. As it happens, this is true of the only cases of colour- 

 blind women having sons that I know of. Two are cases observed 



5.0 



>■ • 



O ^P9^ 

 awiTw 



} 



i 



Fig. li). Pedigrees of two families containing colour-blind female.«, from 

 Mr. Xettleship's collection. 



by Nettleship (see 7). In each case a colour-blind woman had 

 one son. who was coloui'-blind (Fig. 19). The other case is that of 

 Burckhardt (13) a colour-blind woman with three sons, all colour- 

 blind (Fig. 201 



