THEORY OF REVERSION 229 



union is, therefore, always heterozygous purples. 



Thus :— 



pB X Pb = PpBb 



The two whites heterozygous for blueness, Nos. 12 

 and 15, with formula ppBb, will produce two kinds 



m 



a> 



a 



Of 



a 



o c 



d c 



of gametes, pB and pb, so the result of mating them 

 with pink can be most conveniently foretold by 

 means of the four-square table on p. 230, the external 

 characters of the four zygotes produced being shown 

 in the Table alongside. 



The result of this union is, therefore, equal num- 

 bers of purples and pinks. 



