IV. ON THE LATENT CAPACITY FOR MUTA- 

 TION. 



§ 29. REPEATED MUTATIONS ARE THE RESULT OF THE 



SAME INNER CAUSES. 



Hitherto I have confined myself to a mere descrip- 

 tion of the phenomena of mutation in the genus Oeno- 

 thera such as I have directly observed them. . Our task 

 now is to form some idea of the causes of these phe- 

 nomena. 



The attempt to deal with this problem is not only a 

 perfectly legitimate one but the reader would be justified 

 in complaining that my work were incomplete if I did 

 not attempt to deal with it. 



The solution of this problem must, however, be sought 

 among the facts themselves. And for this purpose I 

 shall divide my argument into two parts. The causes 

 which can be dealt with most easily are, naturally, those 

 which operated throughout my experiment, that is the 

 internal and external causes of each of the several muta- 

 tions. But to provide an answer to the questions : what 

 is the cause of the whole phenomenon, and to what is the 

 initiation of the mutation period due Pisa task of a very 

 different nature. And I propose to postpone this to the 

 last section of this chapter. 



