no MENDELISM CHAP. 



tory factor owing to the repulsion between these factors. 

 The nature of the F 2 generation in each case is in har- 

 mony with the above scheme. As, however, it serves to 

 illustrate certain points in connection with intermediate 

 forms we shall postpone further consideration of it till we 



_ discuss these matters, and 

 [9]Ff PP Ii HPPiiW] for the present shall limit 



gives gives 



gametes gametes OUrselvCS to the CXplana- 



F &\ v / fpi tion of tne different be- 



fnl II fPi 



haviour of the FI males 



, . I ! and females when crossed 



FfPpii ffPpli with the Brown Leghorn. 



f*l [<!' And, first, the cross of 



FlG - 2 3- Brown Leghorn female by 



Scheme to illustrate the nature of the Fj gen- 

 eration from the Brown Leghorn hen and FI male. The BrOWn Leg- 

 Silky cock (cf. Fig. 22). 



horn hen is on our hy- 

 pothesis Ffppli, and produces gametes Fpi and fpi. 

 The FI cock is on our hypothesis ffPpli, and pro- 

 duces in equal numbers the four kinds., of gametes 

 fPI, fPi, fpi, fpi. The result of the meetin&of these two 

 series of gametes is given in Fig. 24. Of the eight differ- 

 ent kinds of zygote formed only one contains P in the 

 absence of /, and this is a female. The result, as we have 

 already seen, is in accordance with the experimental facts. 

 On the other hand, the Brown Leghorn cock is on our 

 hypothesis//"/?/?//. All his gametes consequently contain 

 the inhibitor factor, and when he is mated with an FI 



