606 



MESSRS. J. LEWIS BONHOXE A^^D F. W. SMALLEY ON 



Scientifically this result is of but little value, as the hen bird 

 may have made a chance mating with a chequered pigeon ; on the 

 other hand, the youngster was in every other respect (shape and 

 size) a typically wild bird. Unfortunately it met with an accident, 

 so that we haA'e not been able to breed from it. 



Unsatisfactory as this case is, it is obvious that the chequering 

 must in the fir^st place have originated from the Wild Rock 

 Pigeon, and the above is probably a good example of its arising 

 as a mutation. 



A further explanntion may possibly be found in the fact that the 

 chequei'ing cannot show itself except in the piesence of two shades 

 of colour, and that it may be present in many of the pure wild birds 

 but cannot show itself until the colour factor producing the two 

 shades is present, when the chequering will immediately appear. 



This, however, in no w^ay afiects the main issue, namely that 

 when once a Chequer has been produced it is dominant to the pure 

 colour. The mating of two Chequers should therefore produce 

 Chequers or Chequers and Self-coloiu', according to whether the 

 birds are homozygous or heterozgyous for that character. 



As in the case of the Blues, so in the case of the Chequers it 

 appears that fanciers, by continually selecting the best biads for 

 bleeding, have unconsciously been selecting only homozygous birds, 

 with the result that only pure Chequer dominants are to be found 

 in certain strains. We have for instance accurate records of 

 57 matings (Exps. 1-49; 169-172; 175-178) of Chequer to 

 Chequer from which 229 young were produced, and all these 

 without exception were Chequei'S like their parents. It therefore 

 became essential to carry out fui'ther matings with birds that 

 were known to be heterozygous in order to test the dominance 

 of the Chequer chai'acter. This has been done in the matings 

 detailed below, the results of which, as will be seen, approximate 

 very closely to the Mendelian expectation. 



Exp. 



No. 



174. 

 196. 

 197. 

 198. 

 199. 

 200. 

 201. 

 203. 



Ext. 

 A pp. 



06/104- 

 650 

 07/6 

 07/a 

 07/6 

 06/19 

 09/533 

 0824 



Red ] 

 Chequer. ) 

 Blue \ 

 Chequer. \ 

 Grizzle | 

 Chequer. \ 

 Grizzle 7 

 Chequer, j 

 Grizzle ) 

 Chequer. 3 

 Blue \ 

 Chequer. 3 

 Blue 1 

 Chequer. ) 

 Grizzle | 

 Chequer, j 



Gametic 

 Formula. 



From 

 Exp. 



Ext. 

 App. 



06/82 Blue. 

 Grizzle. 



Blue. 



Blue 

 Chequer 



08/13 ' Grizzle. 



I Blue 

 I Chequer. 

 I Blue 

 ! Chequer. 



m\d 



5/ 



08/22 

 08/36 



3/30 j Grizzle. 



Gametic 

 Formula 



Xx 



Xx 

 Xx 



From 

 Exp. 



122 

 153 

 196 

 196 

 196 

 197 

 198 

 197 



Expecta- 

 tion. 



Equality 



3:1 



Equality 



3:1 



3:1 

 E quality 



Result. 

 2 Ch : 2 B 



3:2 



5:3 



2:2 



2:0 



10:1* 



3:3' 



7:2 



Chequering and its absence are represented by X and x. 



* Mating.s for the purpose of testing the extracted recessives from Exps. 200 and 

 201 have been undertaken this year (1911), and prove the recessives to breed true. 



