POLYGENIC SYSTEMS 



genetically, for segregation will have occurred during the formation 

 of gametes from the F^ zygotes. Heritable variation will have been 

 added to the non-heritable, and we must expect therefore that the 



CORFU 



EGYPT 



Fig. i6. — Parents and Fj progeny of a cross between two races of the ladybird 

 Epilachna chrysomclina showing polygenic segregation in respect of the black flecks 

 and the dark colouring between them (after Bauer and Tiniofeeff-Ressovsky, 1943). 



frequency distribution of the Fg will cover a wider range, have a 

 larger spread, than those of the individual parent lines and F^. In 

 biometrical terms the F2 should have a larger variance than parents 

 or Fj, because this variance will have a new, heritable component 



69 



