WINTER EGG PRODUCTION 



401 



eggs during the winter months when eggs bring fancy 

 prices is inherited and that it depends on two pairs of 

 genes. This is an instructive case because it shows that 

 the ability to lay eggs in winter is not an acquired char- 

 acter introduced by the kind of care taken of the flock. 

 One of these genes is in the sex chromosome of which 



Pemalo Parent 



Male F, hybrid 



Female F2 



Fo Male 



F2 Male 



F2 Female 



Fig. 118. — Inheritance of Winter Egg Production Through the 

 Male. One factor for winter egg production is located in the sex- 

 chromosome of fowls. The male has two sex chromosomes and the 

 female one. The diagram shows that the purebred male transmits 

 high egg-laying ability to all his daughters even when mated to a 

 female without this factor (E). Half the F^ females inherit high 

 ability and half do not. All the males inherit the gene (E) but only 

 half of them are pure for it {EE) and therefore suitable sires. 



the male fowl has two active or Z chromosomes and the 

 female only one active or Z chromosome and one inactive 

 or W chromosome (Fig. 118). Hence every daughter re- 

 ceives an active Z from the father but only an inactive 

 W from the mother. Since this gene for high egg-laying 

 is in the Z chromosome, hens inherit this characteristic 

 from the father and not from the mother. Manifestly 



