CENOTHERA AND THE MUTATION THEORY 319 
to indicate a change in the nature of some part of 
the germ-plasm; and the peculiar 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. 
