W. Bateson and R. O. Punnett 



295 



relative distribution of the different characters evidently pointed to 

 some form of repulsion between the normal flower and fertility. Had 

 it not been for the appearance of the single sterile cretin we could have 

 regarded this case as one of complete repulsion between the factors N 

 and F. The problem was to account for the sterile cretin, and at the 

 time we were inclined to regard it as due to an unaccountable failure of 

 repulsion between N and F. Lack of opportunity prevented us from 

 following up this case in 1910, but in the present year we sowed the 

 seed 'of the rest of the F^ plants harvested in 1908 and obtained details 

 of eight more families which are set out in the accompanying table 

 (Table I). 



These records shew that the appearance of a small proportion of 

 sterile cretins is a constant feature in these families and we suggest 

 that their presence may be accounted for as follows. The repulsion 

 between N and ^ is to be regarded as partial, and of such a nature 

 that the series of gametes produced by the ^j plant is NF, SNf, ZnF, nf. 

 Such a series of ovules fertilised by a similar series of pollen grains 

 would give rise to a generation consisting of 33 normal fertiles, 15 

 normal steriles, 15 cretin fertiles, and 1 cretin sterile. As the figures 

 given in Table I shew, this expectation is closely realised by the facts 

 of experiment, and we have little hesitation in regarding this explana- 

 tion as the correct one. Moreover we ar6 inclined to go further and to 

 extend the principle to all cases of repulsion in plants. We consider 

 then that where A and B are two factors between which repulsion 

 occurs in the gametogenesis of the heterozygote formed by union of 



20—2 



