MUTATION. 147 



number of his germ-cells, which made the chicks growing from 

 them blue. In other words, this result of the Andalusian-Wyan- 

 dotte cross tends to show, that blue is dominant to black, in 

 other words that the blues have something more than the 

 blacks. Now there is another fact which proves this. It is well 

 known that in chickens there have been noted several instan- 

 ces where females, heterozygous for a gene produce sons with 

 it and daughters without it, provided her mate does not j>o&. 



Fig. 17. 



Results of crossing a male blue Andalusian to female White Wyan- 

 dotte. 



sess this same gene. A Silver- Wyandotte hen, or Silver Se- 

 bright hen or Assendelver, if mated to a Golden cock will pro- 

 duce golden pullets and silver cockerels. There seems to be a 

 mutual repulsion between the gene which is responsible for 

 female sex and a few other genes. Four or five instances have 

 been noted in the fowl. In all these instances we can see this 

 sex-linked colour inheritance only in cases, where a female of 

 the dominant colour is mated to a male of the recessive colour. 

 It therefore becomes significant that according to a breeder of 



