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 was 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 3:1 ratio. There is therefore no real doubt that it came into existence 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[1] 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 cultures. 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 argument which Gates introduces to the effect that the difference between such quantitative types cannot be represented in terms of presence and absence. We are quite accustomed to the fact that in the rabbit self-colour segregates from the Dutch-marked type. These two types differ in a manner which we may reasonably regard as quantitative. It is no doubt possible that the self-coloured type contains an ingredient which enables the colour to spread over the whole body, but it is, I think, perhaps more easy to regard the Dutch type as a form from which a part of the colour is absent. It may be spoken of in terms I have used, as a _subtraction-stage_ in colour. Following a similar method we may regard _rubricalyx_ as an addition-stage in colour-variation. The fact