380 



W. Bateson. 



A somewhat more i-emarkable case is seen in the combs of 

 fowls. 



Eose comb is dominant to single comb, and pea comb is also 

 dominant to single comb. Rose crossed with pea prodnces an entirely 

 distinct type of comb, the ''walnut" of fanciers. Amongst other pe- 

 culiarities it usually has bristles or small feathers arranged in a 

 band across it in the posterior third, though such bristles are never 

 found in either rose or pea (see Fig. 8 and 9). These F^ "walnut" 

 combs bred together give F., as follows : 9 walnut : 3 rose : 3 pea : 

 1 single 



Fig. 9. Hens with walnut combs of various patterns. In the two birds on the 

 right the depression crossing the back of the comb can bo seen. Upon this the 

 band of hairs in placed. The other three birds have a more lumpj' pattern of 

 ■'walnut". In them the hairs are usually distributed over the posterior end of the 

 comb, without forming a definite baud. 



No single comb was put in. It arises from recombination, which 

 is intelligible as soon as the allelomorphism is correctly represented. 

 The allemorphs are R, the rose-element, r, its absence; P, the pea- 

 element, and p, its absence. The single comb is merely the comb 

 from which both R and P are absent. The distribution of these 

 characters in F« may be usefully shown in a tabular form, as the 

 case is typical of many others. 



