72 THE MENDEL JOURNAL 



grey eyes which contain no visible trace of yellow 

 or brown pigment. The duplex type includes the 

 black, brown, hazel, green, and impure grey and 

 impure blue eyes, ^.e., grey and blue with a little 

 visible yellow and brown pigments present. He 

 found that the simplex type behaves as a recessive 

 to the duplex type ; so that, if one parent had pure 

 duplex eyes and the other had simplex eyes, all the 

 offspring would show duplex eyes. If both parents 

 were of the simplex type, then all the children had 

 simplex eyes. Since the duplex eyes are a dominant 

 type, individuals who possess them may be either 

 carrying duplex only, or they may carry as well the 

 simplex type as a recessive. When both parents 

 have duplex eyes, there are therefore three possible 

 combinations which have to be considered. We 

 may state them symbolically thus : — 



DDxDD, DDxDR, DRxDR 

 That is, we may have a pure duplex married to a 

 pure duplex, or a pure duplex married to a hybrid 

 duplex, or both parents may be of the hybrid duplex 

 type. If we turn back to the tabulation on page 69, 

 we can see the nature and proportion of the expected 

 offspring in these three kinds of marriages, on the 

 assumption that the processes of gametic purity and 

 segregation are operating in Man. 



Let us consider Mr. Hurst's results. When both 

 parents were simplex all the offspring, one hundred 

 and one in number, belonging to twenty pairs of 

 parents, were simplex also. That is, the recessive 

 character breeds true, in spite of the fact that some 



