196 EVOLUTION AND GENETICS 



only A, or only B, or neither A nor B (i.e., ah) in 

 the proportion of 9AB:3A:3B:lah. These four 

 genetic classes correspond to the four recognized 

 blood types IV, II, III, I, as indicated in the 

 diagram. 



Now these sixteen kinds of individuals are found 

 in all populations, so far studied, although in some- 

 what different proportions in different "races." 



It is very simple to tell what the kinds of genetic 

 offspring will be when any one of these sixteen indi- 

 viduals marries any other one. These possibilities are 

 summarized in the following statement taken from 

 Ottenberg : 



Unions of I and I give I 



I "1 I II 

 II II) ' 



^ "M I III 

 III III ) ^' ^^^ 



Unions of II and III give I, II, III, IV 

 IV I I, II, III, IV 



IV II I, II, III, IV 



IV III I, II, III, IV 

 IV IV I, II, III, IV 



Two actual pedigrees, one of them carried throiigh 

 three generations, will serve to illustrate particular 

 cases (fig. 76). 



