J. E. DUBRDEN 165 



Hitherto only one crossing has been secured from parents both of 

 which are clawed and, as shown in Table IV, all four chicks obtained 

 are also clawed. The clawed birds are usually found to be in a 

 heterozygous or simplex condition Avith respect to the claw, in which 

 case the mating of two clawed individuals should give progeny of 

 which three-fourths would be clawed and one-fourth clawless. Naturally 

 not much importance can be attached to a single experiment where the 

 progeny are so few. 



TABLE IV. 

 Breeders : 



Where both parents are clawless the progeny also are usually 

 unclawed, indicating that the genetic factors concerned are either 

 wholly lost to the germ plasm or too weak to express themselves in 

 the soma. 



TABLE V. 



Breeders : 



The results are not invariably so regular as in Table V when both 

 parents are unclawed. A later hatching of eleven chicks from the first 

 breeding pair above, Cock No. 229 and Hen No. 233, contained one 

 chick with a tegumental claw on the right toe and none on the left, 

 the remaining ten being all unclawed as in the earlier hatching ; also, 

 as shown below, out of ten chicks hatched from unclawed parents, nine 

 were like the parents while one had a decided claw on each toe. 



In these two cases we seem to be forced to the conclusion that 

 though no evidence of the claw appears in either of the parents, the 



Jourii. of Gen. ix 11 



