XII 



INTERMEDIATES 



127 



place, and the apparently continuous series of interme- 

 diates is the result of the interaction of the different factors 

 upon one another. The constitution of the FI $ is a //Ppli, 

 and such a bird produces in equal numbers the four sorts 

 of gametes /PI, /Pi, fpl, /pi. The constitution of the FI $ 

 in this case is F/PpIi. Owing to the repulsion between 

 F and 7 she produces the four kinds of gametes FPi, Fpi, 

 /PI, /pi, and produces them in equal numbers. The 

 result of bringing two 

 such series of gametes 

 together is shown in 

 Fig. 28. Out of the 

 sixteen types of zygote 

 formed one (F/PPii) 

 is homozygous for the 

 pigmentation factor, 

 and does not contain 

 the inhibitor factor. 

 Such a bird is as deeply 

 pigmented as the pure FIG. 28. 



^illrv nsrpnt Twn Diagram to illustrate the nature and composition of 



OllKy pdlCIlL. L WU, the F 2 generations arising from the cross of Silky 



again, contain a hen with Brown Leghorn cock " 

 single dose of P in the absence of 7. These are 

 nearly as dark as the pure Silky. Four ' zygotes are 

 destitute of P, though they may or may not contain 7. 

 These birds are completely devoid of pigment like the 

 Brown Leghorn. The remaining nine zygotes show 



