Appendixes 



315 



To distinguish the two kinds of F^ we ought to write 

 AB x ab as AB . ab ; and aB x Ab ought to be written 

 aB . Ab. We must in fact recognize that in the dividing 

 zygotic cell, at some time before segregation is effected 

 probably from the moment of fertilisation a polarity is 

 established ; and that the constituents derived from the two 

 parents are not, in these cases at least, placed indifferently, 

 but are grouped according to their parental origin. 



Hence we may construct the following table : 



For details as to these phenomena see Bateson and 

 Punnett, Proc. Roy. Soc. 1911, vol. 846, p. 3; de Vilmorin 

 and Bateson, ibid. ; Gregory, ibid. ; Bateson and Punnett, 

 Jour. Gen., i. 1911, p. 293. 



The evidence has been obtained from observation of 

 various characters in Sweet Pea ; the relations of tendrilled 

 leaves to the "Acacia" form in Pisum, and of Magenta 

 to Short-style in Primula Sinensis (Gregory). 



Now that we may regard the formation of four cells 

 of composition AB, Ab, aB, ab, as the foundation both 

 of the coupling- and of the repulsion-series the problem 

 is manifestly somewhat simplified. The time, excluding 

 gametogenesis, at which we can most readily imagine 

 four such definite quadrants to be formed is during the 

 delimitation of the embryonic tissues. It is then that the 

 plant is most clearly a single geometrical system. Moreover 

 the excess of gametes of parental composition characterising 

 the coupling- and repulsion-series must certainly mean that 

 the position of the planes of division by which the four 

 quadrants are constituted is determined with regard to the 

 gametes taking part in fertilisation. Though the relative 



