No. 614] 



THE BLUE ANDALUSIAN 



105 



finds it necessary to postulate further that Q is closely 

 linked with m, and M is closely linked with q. Assuming 

 pigment (P) to be present in all cases, he represents the 

 ' 'black" gamete as (mPQ), the " white" gamete as 

 (MPq), and the Fj blues as (mPQ)(MPq). The blue 

 results from bringing M and Q into the same zygote. 

 The monohybrid ratio results when the blues are inbred, 

 however, because of the close coupling of the factors 

 within the parentheses. 



The Hagedoorns (1914, p. 179) also make use of two 

 coupled factors in accounting for the hereditary behavior 

 of blue Andalusians. They state : 



A blue Andalusian fowl, when mated by us to "recessive" white 

 hens did not produce as many blue as white chicks, as should result on 

 the hypothesis, that the white Andalusian is a recessive white (blue and 

 black Andalusians being heterozygotes and homozygotes for one single 



To account for this result they propose a gene A which 

 is present in black Andalusians, but absent in the " white" 

 Andalusian. The blacks, conversely, lack a gene B which 

 is present in the ' 1 whites." 



This factor B, present in a pigmented fowl, actively "dilutes" the 

 colour. It has no effect in the white Andalusians, because these, as they 

 lack A, are not pigmented [italics mine]. We should therefore expect 

 dilute black (blue) young from the cross black X white, which, inter se, 

 would give AB, Ab, aB and ab offspring. Now, there is no evidence 

 that in Andalusians there are ever produced aabb animals, or A ABB. 



or ab gametes are ever produced. In some varieties of fowls this repul- 



Unless their material differs from any that has come 

 under my observation the Hagedoorns err in assuming 

 that what is frequently termed "the white Andalusian" 

 carries no pigment, and Goldschmidt 's suggestion accords 

 more closely with the facts. Further, if the "recessive" 

 white to which they refer was an Andalusian, the produc- 

 tion of equal numbers of blues and blacks from a blue X 

 white (blue-splashed) cross is difficult to understand. 

 The expectation would be equal numbers of blue-splashed 



