94 



SEX AND HEREDITY 



monk, Gregor Mendel, in 1865, though its value was not 

 appreciated till the beginning of the present century. 

 Mendel's law, as it is now called, will best be explained 

 by a concrete example, for which we will choose a case 

 that has been worked out by Bateson in the domestic 

 fowl (Fig. 48) . 



If a black fowl of the right breed is crossed with a 

 white l fowl, also of the right breed (top line of the 



vvvv 



FIG. 48. 



Illustrating the inheritance of feather colour in the Andalusian fowl. 



diagram), the result is a bird of a slatey blue or gray 

 colour (second line of the diagram). This bird is what is 

 known to poultry breeders as the Andalusian fowl. The 

 result of breeding two Andalusians together is shown in 

 line three of the diagram. (To save space, in every case 

 except the first cross, only one parent is shown. It is 

 to be understood that each bird is mated with one of its 

 own colour.) Out of every four chickens produced from 



1 This breed of fowl is not pure white, but has numerous little 

 dark points among its plumage. For convenience, however, it 

 will be called white. 



