134 THE FIRST PRINCIPLES OF HEREDITY 



instance. If we denote the dominant rose quality by R, 

 the dominant pea quality by P, and further, the absence of 

 the rose quality by r and the absence of the pea quality 



A 



B 



C 



Fig. 56. — Combs of Fowls. (After Thomson and Weir.) 



A, single serrated comb; B, rose comb; C, pea comb; D, walnut 



comb. 



by p, then ;' as well as p will denote a single comb, both 

 r and p being recessive to either rose comb or pea comb. 

 R X P gives a walnut ', rxp gives, as R and P are absent, 



