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.

There are many collateral observations recorded both by de Vries and others which have a bearing on the problems, but they do not yet fall into a coherent scheme. For example, we cannot yet represent the formation of laeta and velutina from the various species fertilised by Lamarckiana ♂. That this is not due to any special property associated with the pollen of Lamarckiana is shown by the fact that a species called Hookeri gives laeta and velutina in both its reciprocal crosses with Lamarckiana (de Vries, 1909, p. 3), and also by the similar fact that Lamarckiana ♀ fertilised by the pollen of a peculiar race of biennis named biennis Chicago throws the same types. Before these very complicated phenomena can be usefully discussed particulars must be provided as to the individuality of the various plants used. This criticism applies to much of the work which de Vries has lately published, for, as we now know familiarly, plants to which the same name applies can be quite different in genetic composition.

Attention should also be called to one curiously paradoxical series of results. When the dwarf "mutant" of Lamarckiana which de Vries names "nanella" is used as father on muricata, F1 consists of laeta and velutina in approximately equal numbers. Both forms breed true to their special characteristics, but velutina throws dwarfs of its own type, while laeta does not throw dwarfs. Subsequent investigation of the properties of these types has led to some remarkable conclusions, and it was in a study of these plants that de Vries first came upon the phenomena of dissimilarity between the factors borne by the male and female cells of the same plant, a condition which had been recently detected in the Stocks as a result of Miss Saunders's investigations. The details are very remarkable. We have first the fact that muricata ♀ × dwarf nanella ♂ gives about 50 per cent. laeta and about 50 per cent. of velutina.

As regards Velutina it was shown that:

Talls,Dwarfs,
per cent.per cent.
1. Velutina selfed gave3862
{ Velutina ♀ × dwarf nanella ♂ gave3961
2. {  do.   ×  do.    gave4951
{  do.   ×  do. ♂ derived from velutina gave4357
3. Dwarfs  × velutina ♂ gave—all dwarfs

The three experiments taken together prove, as de Vries says, that the ovules of velutina are mixed, talls and dwarfs, and that the pollen is all dwarf. The condition is almost the same as that of the Stocks. It may be noted also that in the Stocks the egg-cells of the "double" type are in excess, being approximately 9 to 7 of the "single" type, but de Vries regards the two types in velutina as probably equal in number. The figures (169:231) rather suggest some excess of the recessives, perhaps 9:7, and the point would be worth a further investigation.

As regards laeta, by self-fertilisation no dwarfs were produced, but in all other respects it behaved almost exactly like velutina. The ovules are evidently mixed talls and dwarfs, and whether fertilised by dwarfs or by the pollen of velutina, which is already proved to be all dwarf, the result was a steady 50 per cent. of talls and 50 per cent. of dwarfs. The pollen of laeta used on dwarfs gives nothing but dwarfs, and in three series of such experiments 226 dwarfs were produced.

We are thus faced with this difficulty. Since the egg-cells of laeta are evidently mixed, talls and dwarfs, and the pollen used on dwarfs gives all dwarfs, why does not self-fertilisation give a mixed result, talls and dwarfs, instead of all talls? De Vries regards the result of self-fertilisation as showing the real nature of the pollen, and declares it to be all talls, while he represents the behaviour of the same pollen used on dwarfs by stating that in these combinations the dwarf character dominates. This does not seem to me a natural interpretation. I should regard the pollen of laeta as identical with that of velutina, namely dwarf, and I suspect the difficulty is really created by the behaviour of laeta on self-fertilisation. Until a proper analysis is made in which the identity of the different individuals used is recorded, no further discussion is possible.[8]

Other results of a complicated kind involving production of laeta and velutina together with a third form have been published by de Vries in his paper on "Triple Hybrids." To these also the same criticism applies. Some of the observations seem capable of simple factorial representation and others are conflicting.