154 DISTRIBUTION OF THE CHROMOSOMES 



carrying both Z and W, and if such a ZW sperm 

 fertihzed a zero egg of the 55 chromosome female, a 

 56 chromosome female would be produced. Don- 

 caster actually found such a female among offspring 

 from a cross of a female from the 55 chromosome 

 race with wild type male, and he found also the 

 genetic exceptions required on the assumption that 

 this male was a WZZ form. 



