CHAPTER XIII 



MATERIAL PROGRESS 



To preserve itself, Life enjoins upon each genera- 

 tion the imperative task of producing a generation 

 to succeed it. Not a few creatures die as soon as 

 this task is accomplished. But, generally, time 

 remains for the care of oneself, as well as of 

 posterity ; and this may be spent by the indivi- 

 dual, not merely in the search for food, or in the 

 service of the herd, but in provident activities 

 which appropriate or rearrange the things around 

 it. In man, these activities have become so com- 

 plicated and widespread as to overshadow the 

 elementary interests of animal life : he owes to 

 them his elaborate civilization, the contrivances 

 by which he seems to command Nature in place 

 of obeying her. But they are shared, in some 

 degree, by lower animals, and appear to arise 

 from a special instinct that of providence 

 which prompts living creatures not to submit 

 themselves to their environment or slavishly to 

 adapt themselves to it but with active foresight 

 to mould it to their needs. The construction of 

 protective, and often very beautilul, shells is a dis- 

 tinctive feature in the life history of molluscs ; and 

 far below them, in the very lowest ranks of the 

 animal kingdom, organisms which are mere specks 

 of structureless jelly extract materials from the 

 lime or silica in the water around them, for 

 building shells, which, so small as to be invisible 



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