HUMAN EYE COLOUR 47 



nants they produce dominants and hybrids in equal 

 numbers. Thus, if our tall peas of the first hybrid 

 generation had been crossed with dwarfs they would 

 have produced tails and dwarfs in equal numbers ; 

 and if Andalusian fowls had been mated with the 

 whites they would have produced equal numbers of 

 Andalusians and whites. And if hybrid tails had been 

 crossed with pure tails, equal numbers of these two 

 kinds of tails would be produced ; and if Andalusian 

 fowls were mated with the blacks equal numbers of 

 black and Andalusians w^ould have been the result. It 

 is desirable to know this property of hybrids, because 

 if one does not, the existence of families composed 

 of both blue-eyed and brown-eyed children, one of 

 the parents of whom was blue-eyed whilst the other 

 was brown-eyed, does not seem reconcilable at first 

 with the statement that the result of mating duplex 

 (or brown) with simplex (or blue) is invariably duplex. 

 There is, of course, no contradiction, as the reader 

 will now readily see ; in such cases the duplex parent 

 has evidently been a hybrid duplex. 



Moreover, this type of mating — hybrid by 

 dominant, or hybrid by recessive — plays an im- 

 portant part in the Mendelian theory of sex, 

 and in the theory of the origin of Mendelian 

 characters. 



Before quitting the subject of the inheritance of 

 eye-colour in man, it may be useful to set forth the 

 breeding properties of simplex, and of pure and 

 hybrid duplex eyes, in a few short general state- 

 ments. 



