Variation and Heredity 297 



pollen from other species. Here also appeared some of the 

 new species, already mentioned, namely, albida, nannella, 

 lata, oblongata, rubrinervis, and also two new species, elliptica 

 and subovata. 



De Vries also watched the field from which the original 

 forms were obtained, and found there many of the new 

 species that appeared under cultivation. These were found, 

 however, only as weak young plants that rarely flowered. 

 Five of the new forms were seen either in the Hilversam 

 field, or else raised from seeds that had been collected there. 

 These facts show that the new species are not due to cultiva- 

 tion, and that they arise year after year from the seeds of 

 the parent form, O. lamarckiana. 



Conclusions 



From the evidence given in the preceding pages it ap- 

 pears that the line between fluctuating variations and muta- 

 tions may be sharply drawn. If we assume that mutations 

 have furnished the material for the process of evolution, the 

 whole problem appears in a different light from that in which 

 it was placed by (Darwin when he assumed that the fluctuating 

 variations are the kind which give the material for evolution. 



From the point of view of the mutation theory, species are 

 no longer looked upon as having been slowly built up through 

 the selection of individual variations, but the elementary 

 species, at least, appear at a single advance, and fully formed. 

 This need not necessarily mean that great changes have sud- 

 denly taken place, and in this respect the mutation theory is 

 in accord with Darwin's view that extreme forms that rarely 

 appear, "sports," have not furnished the material for the 

 process of evolution. 



As De Vries has pointed out, each mutation may be different 

 from the parent form in only a slight degree for each point, 

 although all the points may be different. The most unique 



