Confonnity to Environment 



vival Is after all comparatively easy, but prog- 

 ress Is the difficult matter. Food Is usually 

 abundant, enemies can be avoided or foiled In 

 many ways. Progress seems usually to have oc- 

 curred only or mainly under the spur of necessity. 

 The great danger seems to be that the animal 

 will develop some structure which Is temporarily 

 advantageous, but which will in time make fur- 

 ther progress impossible. We have seen that 

 this was evidently the mistake of mollusks and 

 Insects, and at the same time of all forms which 

 are represented by the side branches of our gene- 

 alogical tree. All promised well at first. Many 

 attained survival to a greater or less extent. But 

 no one of these attained permanent progress. 

 This was reserved for forms In the middle as- 

 cending stem of the tree, the line leading straight 

 upward to man. 



The great problem for animals and man seems 

 to be not how to get a living, but how to live 

 so as to Insure advance ; not so much to seek out 

 new, easy, and promising radiating lines of live- 

 lihood as avoiding these to follow the one up- 

 ward path. Even extinction is in many cases the 

 result of so complete conformity to conditions 

 which arc transitory that, when these change, the 



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