Active Causes of Organic Evolution 201 



of conditions arise mainly, as we would consider, by environal 

 action, and proenvironal response, though in part also by utili- 

 zation of accessory developments, which in their summated 

 effect on the organism cause it to advance in physiological 

 and in morphological detail, and in the process to vary or 

 depart from other individuals that it once resembled, but which 

 fail to show like progressive advance. 



If such advance gives added dominance to the organism it 

 will tend to survive alongside its former neighbors, wliich will 

 tend to be eliminated. It was this phase of Selection that 

 Darwin emphasized thus: '*If variations useful to any organic 

 being ever do occur, assuredly individuals thus characterized 

 will have the best chance of being preserved in the struggle 

 for life; and, from the strong principle of inheritance, these 

 will tend to produce offspring similarly characterized. This 

 principle of preservation, or the survival of the fittest, I have 

 called Natural Selection. It leads to the improvement of 

 each creature in relation to its organic and inorganic conditions 

 of life, and, consequently, in most cases, to what must be re- 

 garded as an advance in organization." 



In this case, then, each such creature shows, not a balanced 

 state alongside summated environal forces, but it so rises above 

 or excels the possible balanced, not to say disintegrating, ac- 

 tions of an environment that advance or new integration is 

 effected. Instances of such are everywhere quoted and dis- 

 cussed in works on evolution. 



The third or negative or eliminating side of Selection has 

 been greatly discussed. For the writer no more striking in- 

 stance can be cited than the connection and slowly disin- 

 tegrating action to the point of elimination, of ectotrophic or 

 endotrophic fungi, on those groups of flowering plants with 

 which these fungi are associated. Here species of the higher 

 fungi penetrate the roots of many flowering plants, evidently 

 by chemo tactic action. Then, as the writer would interpret 

 the phenomena, they live not a purely parasitic but rather 

 a symbiotic existence, in which both organisiiis are more or 

 less helpful to each other. But by extremely slow degrees 



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