216 POPULAR SCIENCE MONTHLY. 



which especially differs from those we have been studying, by the fact 

 that even when artificially fertilized, with the utmost precautions, the 

 mutation is not stable. The majority of its descendants belong to 

 three groups: 0. scintillans, 0. oblonga, 0. Lamarckiana. As com- 

 pared with the wonderful stability which we encountered in the pre- 

 ceding mutations, the lability of this one — which at the same time 

 seems to follow a certain law — is a most remarkable phenomenon, the 

 origin and the significance of which have still to be traced. 



We have now seen that for a number of years de Vries has been 

 able, by his careful and skilful experiments, actually to witness the 

 very process of the origin of species in nature. On the particular spot 

 near Graveland, where he first noticed the process of mutation in 

 nature, it had, of course, been going on even before his first observa- 

 tions. He here encountered, besides the 0. Lamarckiana, a second spe- 

 cies, the 0. laivifolia, with which he also made experiments in the 

 Amsterdam hortus, and which also produced numerous mutations, some 

 of them identical with those obtained from 0. Lamarckiana. 



Especially important was the irrefutable demonstration of the fact 

 that the process of mutation does not appear as one single specimen 

 which gives rise to a constant variety, but that it again and again re- 

 peats itself in every generation in a certain percentage, and that abso- 

 lutely the same 'mutants' appear — even though in varying quantities. 

 The individual mutants thus find their chance of surviving consid- 

 erably increased and, as soon as a slight change in the outward cir- 

 cumstances occurs, any mutation, which at the outset was in the mi- 

 nority as compared with the parent species, may slowly but surely 

 become the majority. It is constantly getting a fresh supply from the 

 parent species and, as soon as it shows itself better adapted to the cir- 

 cumstances, it may finally supplant the parent species entirely. 



This struggle for existence does not occur between individuals of 

 the same species, but between the mutations and the parent species. 

 As long as the mutation has not appeared, there can be no question of 

 the origin of a new species; the species is then constant, and only sub- 

 mitted to fluctuating variability, which can produce local races (not 

 elementary species) under the constant cooperation (either artificial 

 or natural) of selection, but which never leads to the formation of 

 species. During a period of mutation a modification of the species is 

 not always a necessary consequence; for in many cases the parent 

 species will prove to be the fittest, and the mutations will then none 

 of them be permanent. 



The fact has been established by de Vries that in the natural life 

 of a wild plant a series of phenomena occurs which justifies us in saying 

 that he has made us see and actually touch the origin of species, 

 whereas Darwin had made us understand it. 



