258 MR. J, T. CUNNIKGHAM ON 



In view of the subdivision of the pigmentation cliai\acter proved 

 by my results, the remarksof Bateson and Punnett on p. 201 of their 

 paper are somewhat curious. They state that the F^ birds, either 

 of both sexes or of the male sex only, according to the mating, 

 in respect of the intensity of their pigmentation might belong to 

 either of their three classes, slight, some, or moderate, and that 

 their experience has been that these classes grade very much into 

 one another. Further on they remark that it would be possible 

 to choose birds of the F^ generation from Silky 5 x Brown Leg- 

 horn cJ , and to arrange them in a seizes exhibiting continuous 

 gi'adation from full pigmentation to none at all. " Yet we now 

 know," they assert, " that such a series is due to the intei-action 

 of three definite factors, inclusive of the sex factor, and that the 

 continuity of variation manifested is in reality founded upon a 

 discontinuous basis." It seems to me that this is a misuse of 

 words : we know nothing of the kind. What we know is the 

 continuous gradation ; and even apart from the results of my ex- 

 periment, the discontinuous basis to which the authors refer is 

 purely hypothetical. Moreover, one cannot help asking, in the 

 light of the above quoted remarks, what value is to be attached 

 to the distinction of the three degrees of pigmentation, full, some, 

 and none, on the numbers placed under which degrees the validity 

 of the factors assumed by the authors entirely depends. 



In view of the failure of complete segregation in the two 

 characters dealt with in this and the preceding paper, it is natiu-al 

 to consider whether any of the other characters present in the two 

 forms crossed also fail to segregate. This point is more difficult 

 to decide in the other characters. Thei^e could be no doubt that 

 the white plumage and the unpigmented skin were recessive with 

 a trace of the dominant character, but in other characters any 

 condition short of complete absence might possibly belong to the 

 heterozygote. 



The double hallux. This character obviously does not behave in 

 the normal Mendelian fashion. In F, the double hallux is 

 dominant but not completely so : in my F, cock both feet were 

 normal, in the hen both feet had the double hallux. In F^ there 

 are nine normals to one with double hallux, but no intermediates. 



Feathering of legs. There appear in the F^'s to be two homozygous 

 dominants, six heterozygous, and two recessives. If this is the 

 correct interpretation, one of the recessives contained a trace of the 

 dominant character, the degree of feathering being infinitesimal, 

 only a few very minute feathers between the large scales. I am 

 inclined to think that the only specimen recorded as having quite 

 clean legs had really a trace of the character, for although no actual 

 feathers were visible, the lower edges of the scales showed a slight 

 ridge. 



Crest. There are two specimens, Nos. 1 and 7, one cock and one 

 hen, with no trace of crest and the rose comb pointed behind. 

 These seem to be pure recessives showing complete segregation. 



