22 



MEXDELIAN SEGREGATION 



(mTTTTTD 

 (TimTTTD 



VESTIGIAL GRAV 



LONG 



EBONY 



GRAY 



(UIIIIIID 



(LJIIIIIID 



GAMETOGENESIS orF^ 



FIG. 11. Vestigial gray by long ebony fiy, to illustrate the inheritance 

 of two pairs of characters. The factor for vestigial is carried by the 

 second, the factor for ebony by the third chromosome pair. In the lower 

 part of the figure the two modes of separation, of the two pairs of chro- 

 mosomes involved here, are represented. Four kinds of gametes result. 

 These four kinds combine at random in fertilization, so that 16 classes 

 are produced in F 2 , as shown in the next figure. 



