CENOTHERA AND THE MUTATION THEORY 319 



to indicate a change in tlie nature of some part of 

 the germ-plasm; and the pecuUar behavior of 

 (Enothera makes it very unfavorable for the study 

 of this phenomenon, or for the proof of its occurrence. 

 Fortunately, however, there is abundant evidence 

 that mutations in the germ-plasm do occur in other 

 forms, where they cannot possibly be explained as 

 recombination products. 



