EVIDENCES OF MUTATION 79 



Fluctuating variability, as a rule, is subject to regression. The seeds 

 of the extremes do not produce an offspring which fluctuates around their 

 parents as a center, but around some point on the line which combines 

 their attributes with the corresponding characteristic of their ancestors, 

 as Vilmorin has put it. No regression accompanies mutation, and this 

 fact is perhaps the completest contrast in which these two great tj-pes of 

 variability are opposed to each other. 



The offspring of my mutants are, of course, subject to the general laws 

 of fluctuating variabihty. They vary, however, around their own mean, 

 and this mean is simply the tj^De of the new elementary species. 



4. The mutations take 'place in nearly all directions. 



Some are larger, others smaller than the parent species; 

 some more vigorous and productive, others less so; some are 

 more heavily pigmented, others less so; some can survive in 

 competition with the parent form, others cannot. There is 

 no evidence of adaptive modification, or modification con- 

 trolled by the environment for the benefit of the species. 

 The variation is in all directions. 



The facts upon which De Vries bases these generalizations 

 have been verified in the main by a number of workers in 

 different parts of the world, notably in this country where 

 several botanists have studied the seedlings of Lamarck's 

 evening primrose. But the facts are not interpreted in the 

 same way by all observers. 



One view accepts the facts at their face value, including 

 the regularity of the occurrence of the same mutation in 

 successive generations, and its entire distinctness from the 

 parent form, but maintains that 0. Lamarckiana is a hybrid 

 plant, not a pure species, and that the so-called mutation is 

 only a new illustration of the splitting up of a hybrid into new 

 forms, many of which are constant, a thing which is known 

 frequently to occur following hybridization. 



In support of this view it may be said that 0. Lamarckiana 

 has not been found growing wild in this country, its supposed 

 place of origin, though careful search has been made for it. 

 On the other hand 0. Lamarckiana has for many years been 

 growing wild in certain English stations, notably on the sand 

 hills north of Liverpool, and there are good reasons for be- 

 lieving that the Lamarckiana first brought out by seedsmen 



