44 BREEDING 



pigment, tlie purple of the uvea behind the iris 

 and a varying amount of brown pigment in front 

 of it. 



If the reader prefers the use of familiar terms 

 duplex may be spoken of as brown and simplex as 

 blue, and in nine cases out of ten the application of 

 these common words will be correct ; but it must 

 be remembered that there are some eyes which would 

 be described as blue in common parlance, but which 

 really fall into the duplex class because they possess 

 a trace of brown pigment. 



The result of a union between a person with a pure 

 duplex eye and one with a simplex eye is a child 

 with a duplex eye. Duplex, therefore, is dominant 

 and simplex is recessive. The generation produced 

 by the union of such hybrid duplexes, as we may 

 call them, consists of three duplex and one simplex 

 in every four. These simplexes breed true, i.e. 

 produce offspring with simplex eyes only, when mated 

 with their like. Of the three duplexes, one, the pure 

 dominant, will, if mated with another of the same 

 kind produce pure duplexes only. The other two 

 duplexes are hybrid, and when mated with similar 

 hybrid duplexes will produce duplexes and simplexes 

 in the ratio of three to one. The reader may make a 

 scheme of the mode of inheritance of human eye- 

 colour by substituting duplex for tall, and simplex 

 for dwarf in the frontispiece. 



At the beginning of the last paragraph I spoke of 

 " the result of a union between ... a "pure duplex eye 

 ..." By " pure " I do not mean anything which 



