R. C. PUNNETT 83 



(hooded white long) x E. H. round were given in Report IV, Evol. 

 Gomm. Roy. Soc. 1908, p. 14. The general result shewed "coupling" 

 between B and L, together with " repulsion " between B and E, and 

 between L and E, a result which from the nature of the mating was to 

 have been expected. It was pointed out in an earlier account (R. E. C. 

 IV. p. 11), that the two classes purple round and red long were less 

 numerous than was expected on a 7 : 1 basis, and at the time an ex- 

 planation was suggested on the grounds of some of the families being 

 on a 7 : 1 basis and others on a 15 : 1 basis. The recent publication of 

 Trow's Paper (16) on reduplication series has put the matter in a new 

 light and we shall return to this case later in discussing his suggestion 

 (p. 91). For the moment we may turn to Table VI which adds further 

 data by the inclusion of a number of F., and F^ families derived from 

 the cross white hooded Bush long (BeL) x white erect Cupid round 

 (bEI). The F^ families were given in the earlier account ((3), p. 12) 

 and were there regarded as a case of coupling on a 15 : 1 basis. Fuller 

 experience however has led to the conclusion that they should be classed 

 with the material derived from the original cross Blanche Burpee x 

 Emily Henderson. Three further families ('08, 89, 93, 114) have 

 been added derived from other material in which the mating was of 

 the nature BeL x bEI. 



Consideration of each pair of the three factors taken separately 

 shews their relations to be as follow^s : 



(a) BL : Bl : bL : bl :: 3006 : 164 : 212 : 843, 



(/S) 



(7) 



Evidently (^) and (7) are " repulsion " forms of reduplication in 

 which the zygotic series 1n^ -\- lAB : w- - lAb : w^-laB : lab is de- 

 rived from a gametic series lAB : (n — l)Ab : {n — l)aB : lab ((6), 

 p. 295). An approximation to the value of n in such cases is most 

 readily obtained by dividing the last term in the zygotic series into 

 one of the two middle terms. This gives the approximate value of 

 n- — 1 from which the value of n may be readily deduced. 



In the case of (7) -^j — = — ^— whence ?i- - 1 = 169 and n - ap- 

 proximately 13. Hence the zygotic series (7) is given most nearly by 

 a gametic series lEL : 12EI : 12eL : lei. 



In (/3) there is no individual lacking both B and E, and all that can 

 be stated of n is that it is almost certainly > 32. 



