the _parental combinations_ are in excess. This excess almost certainly follows the system indicated by the accompanying table. In the general expressions _n_ is half the number of gametes required to express the whole system. Now if we imagine that sex-factors are involved with the others concerned in such a relationship as this we have a system of distribution approximating to that found in _biennis_ and _muricata_. The difference in reciprocals is represented in a not improbable way. It cannot yet be said that the rarer terms in the series are formed at all, and perhaps they are not. As we pointed out in our discussion of these phenomena, the peculiar distribution of factors in these cases must be taken to mean that the planes of division at some critical stage in the segregation are determined with reference to the parental groups of factors, or in other words, that the whole system has a polarity, and that the distribution of factors with reference to this polarity differs according to the grouping of factors in the gametes which united in fertilization to produce the plant. Subsequent proliferation of cells representing certain combinations would then lead to excess of the gametes bearing them. It is on similar lines that I anticipate we shall hereafter find the interpretation of the curious facts discovered by de Vries, though it is evident that a long course of experiment and analysis must be carried through before any certainty is reached. The work must be begun by a careful study of the descent of some single factor, for example, that causing the broader leaf of _biennis_, and we may hope that the study of _Oenothera_ by proper analytical methods will no longer be deferred. We have now to return to the relations of _laeta_ and _velutina_. These two forms, it will be remembered are frequently produced when _Lamarckiana_ or one of its derivatives is used as male, and the most unexpected feature in their behaviour is that _both breed true as regards their essential characteristics, on self-fertilisation_. If one only bred true the case might, in view of the approximate numerical equality of the two types, be difficult to interpret on ordinary lines, but as both breed true it must be clear that some quite special system of segregation is at work. What this may be cannot be detected on the evidence, but with the results from the _biennis-muricata_ experiments before us, it is natural to suspect that we may here again have to recognise a process of allocation of different factors to the male and female sides in _laeta_ and _velutina_. That some such system is in operation becomes the more probable from the new fact which de Vries states in describing the group of characters which he calls _conica_, namely that this type is the same as that of _velutina_.