DIVERGENCE 297 



could then develop into a mighty tree, whose branches could all 

 remain in blooming condition, so that the now isolated extremest 

 species would be united with all others through gradatory forms. 



"The adaptation resulting from the effects of the struggle for 

 existence is absolutely not identical with advance for higher 

 standing; more complex forms are by no means always better 

 adapted to outward conditions than the lower ones. The evolution 

 [here used by the author as synonymous with advance or pro- 

 gressive complexity] of organisms cannot be explained in a 

 purely mechanical way. In order to explain the origin of higher 

 forms from lower forms it is necessary to postulate in the organ- 

 isms a special tendency to advance which is nearly related to, or 

 identical with the tendency to vary, which tendency compels the 

 organisms to advance so far as the outward conditions permit." 



It may be wise to add that such views have not met 

 with acceptance even among the most urgent anti- 

 Darwinians. 



In endeavoring to account for the origin of species 

 otherwise than by natural selection, the theory of "Muta- 

 tion" has taken a strong hold on the mind of the day, and 

 has found a champion in Hugo De Vries, a strong anti- 

 Darwinian. This Belgian botanist had the good fortune to 

 discover a plant, CEnothera lamarkiana, a variety of prim- 

 rose, at a time when it appeared to undergo a sudden trans- 

 formation, diverging from its customary type to a larger 

 and quite different one. The new form, which differed 

 sufficiently to constitute a new variety, if not a new 

 species, appeared to undergo the change "spontaneously," 

 i.e., without any accountable cause. It was, in other 

 words, a " sport" of Nature. The new individual, how- 

 ever, bred true, without any tendency to revert to its 

 original type, and has remained true. This has led De 

 Vries to the conclusion that new species arise spontane- 

 ously as "freaks" or "sports," and that such new forms 

 appear infrequently in the history of every species and 

 serve as points of departure from the old type. Accord- 

 ing to this theory, which seems to be widely accepted 

 ,by scientists of the present day, species arise suddenly, 

 by mutation, and not gradually by natural selection. 

 De Vries showed quite clearly that there was a distinct 

 difference between the fluctuating and non-heritable 



