ii4 PROBLEMS OF GENETICS 



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 cap- 

 able of simple factorial representation and others are conflicting. 



Taking the work on Oenothera as a whole we see in it con- 

 tinually glimpses of order which further on are still blocked by 

 difficulties and apparent inconsistencies. Through such a stage 

 all the successful researches in complicated factorial analysis 

 have passed and I see no reason for supposing that with the 

 application of more stringent methods this more difficult set of 

 problems will be found incapable of similar solutions. To 

 return to the original question whether in Oenothera we can claim 

 to see a special contemporaneous output of new species in actual 

 process of creation, it will be obvious that while the interrelation 

 of the several types is still so little understood, such a claim has 

 no adequate support. It is true that many of the "mutants" 

 of Lamarckiana can well pass for species, but this is equally true 

 of many new combinations of pre-existing factors as we have 

 seen in Primula Sinensis and other cases. Still less can it be 

 admitted that these facts of uncertain import supply a justi- 

 fication for the conception which has played a prominent part 

 in the scheme of the Mutationstheorie, namely that there are 

 special periods of Mutation, when the parent-species has peculiar 

 genetic properties. To conclude: The impression which the 

 evidence leaves most definitely on the mind is that further dis- 

 cussion of the bearing which the Oenotheras may have on the 

 problem of evolution should be postponed until we have before 

 us the results of a searching analysis applied to a limited part of 

 the field. In such an analysis it is to be especially remembered 

 that we have now a new clue in the well-ascertained fact that the 

 genetic composition of the male and female germ-cells of the 



8 Zeijlstra in a recent paper announces that many nanella plants are the subject 

 of a bacterial disease to which he attributes their dwarfness. I gather that this 

 does not apply to all nanella plants and that some are dwarfs apart from disease. 

 The matter may no doubt be further complicated from this cause. 



