BREEDING FOR COLOR AND PLUMAGE MARKINGS 261 



Double Matings. Before discussing color variations in detail, 

 it is necessary to understand what is meant by the term " double 

 mating." Double matings are quite different from the reciprocal 

 crosses described elsewhere. They have been developed largely 

 through the sexual dimorphism which is so pronounced hi most 

 breeds of poultry, and especially through the desire of breeders to 

 exaggerate this difference between the sexes. These are often 

 designated as cockerel and pullet matings. 



Examples of such exaggerated differences are found between 

 the hen and cock birds of Dark Brahmas. It is the desire to per- 



FIG. 132. ,A difference in color pattern due to sex an example of sexual dimorphism. 



feet the penciling of the hens, while in the males it is to group the 

 colors in masses. In order that this difference may be highly 

 developed, the practice is to make two matings, one for females 

 and the other for males. To produce females the practice is to 

 mate the best penciled hens with a cock bird which shows as 

 much lacing as possible. To produce males the darkest hens are 

 mated with cock birds which show as little lacing as possible. 



The sexual difference may be noted in Barred Plymouth Rocks, 

 the males showing narrower bars and being lighter throughout, 



