ARE RECESSIVES LOSSES OF GENES? 



73 



necessarily that the allelomorphs of these genes are ab- 

 sences. The allelomorphs may be only other genes that do 

 not give rise either to pea or to rose comb. 



Fig. 43. 



Combs of domesticated races of fowls, a, single comb; b, pea 

 comb; c, rose comb; d, walnut comb (the hybrid or Fj type when 

 pea and rose are crossed). 



The result may be stated in another way that may make 

 the situation more obvious. If we assume that the wild 

 jungle fowl, from which our domesticated races have 

 come, had a single comb, and that at some time a domi- 

 nant mutation occurred that gave a pea comb, and at 



