The Hypothesis of a Premutation Period. 491 



least conceivable mutations did not appear — e. g., white 

 flowers. 



Our conclusion is therefore that only what is already 

 present in a latent state can appear during the period of 

 mutation; but nothing or almost nothing which is not 

 already there. 



Oenothera Lamarckiana would appear therefore to 

 be laden with a certain number of latent characters, which 

 it splits off if we may so express it, from time to time. 

 Thus it may perhaps sometimes *'split off" plants which 

 lack one or more such latent potentialities, and therefore 

 be no longer mutable in respect of these. If these indi- 

 viduals should be the only ones which ultimately survive, 

 the mutation period would be at an end. 



When and how did the latent characters arise? Their 

 origin was the real beginning of the period of mutation, 

 and will be referred to in future, for the sake of brevity, 

 as premutation. This premutation or the first origin of 

 the potentialities of the later mutations is evidently an 

 event which takes place in a latent state. It may be ac- 

 companied by mutations; though that does not seem to 

 be essential. It can of course only be made known to us 

 by mutations ; but it may be already there before we can 

 perceive any trace of it. 



We may assume that all potentialities which are mani- 

 fested during a period of mutation arise either succes- 

 sively or at once. It seems possible that the whole group 

 of new potentialities might arise in the lifetime of a 

 single individual, or perhaps in the brief period of its 

 sexual life. But it is also possible that several genera- 

 tions may be necessary for the process. 



The older plant-breeders thought that it would be 

 possible to upset the internal economy of a plant in sucli 



