92 HEREDITY AND VARIATION 



spread in hundreds over the field. It had been extremely prolific 

 in its freedom, but that was not its chief interest. 



Its chief interest was its changefulness. It had, so to speak, 

 frolicked in its freedom. Almost all its organs were varying — 

 as if swayed by a restless tide of life. It showed minute fluctua- 

 tions from generation to generation ; it showed extraordinary 

 freaks like fasciation and pitcher-forming ; it showed hesitancy 

 as to how long it meant to live, for while the majority were 

 biennial, many were annual, and a few were triennial ; best of 

 all, it showed what can hardly be otherwise described than as 

 new species in the making. 



It is possible that the prolific multiplication in a new environ- 

 ment may have had something to do with the awakening of the 

 impulsive mutability. 



In 1887, a year after his discovery of the potato-field, De Vries 

 found two well-defined new forms — a short-styled 0. brevistylis 

 and a beautiful smooth-leaved 0. teyi/o/z«— distinguishable from 

 the parent 0. lamarckiana in many details. He hailed these 

 as two new " elementary species," * and he applied one of the 

 crucial tests of specific or subspecific rank : Did they breed true ? 

 He found that this was so ; from their self-fertilised seeds similar 

 forms arose. Neither of the two new forms was represented in 

 the herbaria at Leyden, Paris, or Kew ; neither had been described 

 in the literature of Onagracese. They seemed to be distinctively 

 new. It is interesting to note that in 1887 there were few 

 examples of these two new elementary species, and that each 

 occurred on a single plot in the field. The impression conveyed 

 was that each had arisen — by a sudden mutation — from the seed 

 of an individual parent. 



The next chapter in the famous investigation began with 

 a transference of samples of the new forms and the parent 



* By an " elementary species " is meant simply a group of individuals 

 which agree with one another and differ from other groups in a certain 

 number of characters, normally constant through successive generations. 



