MUTATIONS 129 



example, is the smooth leaf or stem considered as having lost a 

 character as compared with its downy relative ? 



5. "The same new species are repeatedly produced," that is 

 to say, the same new forms arise again and again, showing that 

 the tendency to their production is inherent and. persistent. 

 " This is a very curious fact," remarks De Vries. " It embraces 

 two minor points, the multitude of similar mutants in the 

 same year, and the repetition thereof in succeeding generations. 

 Obviously there must be some common cause. This cause must 

 be assumed to lie dormant in the Lamarckians of my strain, etc. 

 . . . The germs of the oblonga, lata, and nanella are very irritable 

 and are ready to spring into existence at the least summons, while 

 those of gigas, rubrinervis, and scintillans are far more difficult 

 to arouse." May not the same be true in nature generally, and 

 may not the same strain arise again and again, commonly fail- 

 ing to persist because as a rule all conditions are against it ? 



6. Mutability is distinct from fluctuating variability. Darwin 

 regarded the new type as built up by the operation of selection 

 upon fluctuating variability, establishing a new type by the 

 gradual accumulation of favorable variation, all others (inter- 

 mediates) being exterminated. De Vries regards mutability as 

 distinct from fluctuating variability, and considers that he has 

 presented experimental evidence to show that it is entirely com- 

 petent to give rise to new forms suddenly, without intermediates 

 and without the aid of selection. He of course believes that all 

 types, both old and new, are subject to fluctuating variability, 

 and that through selection some improvement is possible, but that 

 this is not the sole or principal method of securing new types. 



7. " The mutations take place in nearly all directions." Some 

 are larger, some are smaller than the parent ; some stronger, 

 others weaker ; some plainer, others more brilliant. The species 

 is not, therefore, drifting ; it is sending out new types from all 

 sides. 



SECTION IV AMERICAN EXPERIENCES 



The experiments of De Vries are strongly confirmed by the 

 experience of breeders, especially in the production of new varie- 

 ties of fruits and vegetables. Many of these have been so long 



