Appendixes 315 



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

 ABy^ab as AB . ab\ and aB v. 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 : 



Partial 



repulsion 



from zygote 



of form 



Aby.aB 



Partial 

 coupling 

 from zygote 

 of form 

 ABy.ab 



Gametic series Number Number of Nature of zygotic series 



^,«_ ^ ^ of gametes zygotes ^ ■ ■ '^ _— — ^ 



AB Ab aB ab '\n series formed AB Ab aB ab 



(«-i) («-i) I in 4«2 2«2+i n^-\ it^-i 



31 31 I 64 4096 2049 1023 1023 



t5 15 

 7 7 



32 1024 513 255 255 

 16 256 129 63 63 



3 31 « 64 33 15 15 



I I I 4 16 9 3 3 



f 3 I I 3 8 64 41 7 7 9 



71 I 7 16 258 177 15 15 49 



t5 I I '5 32 1024 737 31 31 225 



31 I I 31 64 4096 3009 63 6i 961 



63 I I 63 128 16384 12161 127 127 3969 



^(«-i) I I {n-i) in 4«2 3«2-(2;;-i) in-\ in-i n'^-{2n-\) 



For details as to these phenomena see Bateson and 

 Punnett, Proc. Roy. Soc. 191 1, vol. 84 b, p. 3; de Vilmorin 

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

 Jour. Gen., i. 191 1, 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 



