490 On the Latent Capacity for Mutation, 



§ 31. THE HYPOTHESIS OF A PREMUTATION PERIOD. 



The mutations of Oenothera Laniarckiana which have 

 been described in this section form so circumscribed a 

 group of phenomena that the question as to their origin 

 and causes can hardly be avoided. 



There can be no doubt that I have neither witnessed 

 the beginning nor the end of these mutations. I have 

 evidently only been able to follow a section of the whole 

 period of mutation.^ 



But in attempting to form some conception as to the 

 mode of origin of such a period we must leave the sphere 

 of observation for that of hypothesis. If the purpose 

 of doing so was nothing more than the mere elaboration 

 of the theoretical conceptions I should drop it at once. 

 But, as a matter of fact, what we want is a working 

 hypothesis which may result in bringing the origin of 

 such a period within the range of experimental inquiry. 



In order to work out some such hypothesis we must 

 look to the facts to indicate what we must expect to find, 

 that is what we really have to investigate. 



We came to the conclusion in the preceding sec- 

 tions that a mutation is not the result of the sudden 

 origin of a new character but of the manifestation of one 

 already present in a latent condition. During the whole 

 period of mutation the capacity for producing dwarfs 

 is, apparently, present in all individuals. So is that for 

 giving rise to examples of lata. On the other hand the 

 capacity for producing O. brevisfylis and 0. laevifolia 

 was, presumably, absent during the whole period of my 

 experiments. Moreover a number of possible, or at 



^ Which is still lasting (1908). 



