42 BREEDING 



because they also include the green, the grey, and 

 the hazel eyes. 



A duplex eye is, as we have said, any eye in 

 which there is brown pigment in front of the iris. 

 This brown pigment exists on the top of the fibrous 

 tissue of the iris which appears blue ; so that if we 

 could dissolve away the brown pigment from a dark 

 brown eye the blue would appear underneath. There 

 is every degree in the amount of this brown pigment. 

 If there is very little indeed, it usually exists as a 

 thin ring round the pupil, all the rest of the iris 

 being blue. This has been called a ring-duplex, and 

 if there is a mere trace of the brown pigment, a duplex 

 eye of this kind would doubtless often pass as a 

 " grey " or even " blue " eye. If there is more of 

 the brown pigment, a " hazel " eye is very often the 

 result. In another form of duplex eye the brown 

 pigment is distributed in patches over the blue 

 ground colour which can be seen between the patches ; 

 " hazel " eyes are also often the result of this arrange- 

 ment. When there is a very thin uniform layer of 

 brown pigment, the colour of this (a sort of yellow 

 ochre) blends with the blue of the background, which 

 can be seen through, and a " green " eye is the result. 

 And, finally, there are the self-coloured duplex eyes 

 in which the brown pigment is spread uniformly 

 over, and completely concealing, the blue back- 

 ground, giving the various intensities of brown eye, 

 according to its abundance. 



A simplex eye is one in which there is no brown 

 pigment on the anterior surface of the iris. All the 



