92 PROBLEMS OF GENETICS 



In the case of the Chinese Primrose (Primula Sinensis) one 

 dominant factor has been introduced in modern times, probably 

 within the last six years at most. This is the factor which 

 causes suppression of the yellow eye, giving rise to the curious 

 type known as " Queen Alexandra." Mr. R. P. Gregory's 

 experiments proved that this was a very definite dominant, and 

 the element responsible for this development is undoubtedly an 

 addition to the original ingredient-properties, with which the 

 species w r as endowed. Unfortunately, as happens in almost every 

 case of the kind, the origin of this important novelty appears 

 to be lost. Its behaviour, however, when crossed with various 

 other types is that of a simple dominant giving an ordinary 3 : I 

 ratio. There is therefore no real doubt that it came into exist- 

 ence by the definite addition of a new factor, for if it was simply 

 a case of the appearance of a new character made by combination 

 of two previously existing complementary factors we should 

 expect that when Queen Alexandra was self-fertilised a 9 : 7 

 ratio would be a fairly common result, which is not in practice 

 found. 



In Oenothera Gates l has observed the appearance, in a large 

 sowing of about 1 ,000 Oenothera rubrinervis, of a single individual 

 having considerably more red pigment in the calyx than is usual 

 in rubrinervis. The whole of the hypanthium in the flowers of 

 this plant was red instead of green as in rubrinervis, and the 

 whole of the sepals were red in the bud-stage, except for small 

 green areas at the base. This type behaved as a dominant over 

 rubrinervis, but so far a pure-breeding individual was not found. 

 Admittedly the variation of this plant from the type of rubrinervis 

 can be represented as one of degree, though there is a very 

 sensible gap in the series between the new form which Gates 

 names "rubricalyx" and the reddest rubrinervis seen in his cul- 

 tures. It must certainly be recognised as a new dominant. 

 Gates, rightly as I consider, regards the distinction between 

 rubrinervis and rubricalyx as a quantitative one, and the same 

 remark applies to certain other types differing in the amount of 

 anthocyanin which they produce. I do not understand the argu- 



i Gates, R. R., Zts. f. Abstammungslehre, 1911, IV, pp. 341 and 361. 



