NONSUCH 



fifty million years before 1931, saw genera of snails 

 living and thriving, unchanged from these alive to- 

 day — at a time when no bird or mammal or flower- 

 ing plant had yet appeared. In the Upper Cambrian 

 mollusks were abundant, and a few well-developed 

 and going snails were living in the Lower Cam- 

 brian — five hundred million years back. Now look 

 at our periwinkle with renewed respect; his an- 

 cestors, with shell, muscles, movement and life 

 closely similar to his, were alive when the earth 

 itself was only three-quarters evolved. 



We are reasonably certain that the higher evolu- 

 tion had little impetus in the deep sea; conditions 

 there were too stable and unchanging, competition 

 was hardly felt: Not until the hard rock and the 

 shifting sands of the shore were encountered, the 

 crash and drag of waves, the submersion and ex- 

 posure of varying tides, enemies in pool and air — 

 these demanded change, adaptation, extermination, 

 and progress. 



As yet we know nothing definitely about the very 

 early ancestors of our snail, but as we have seen, 

 even in the early eons of the sea he had achieved a 

 shell, and when he crawled shoreward and out upon 

 primeval mud-flats, it was as if he dragged with him 

 a bit of the unchanging deeps. As long as food was 

 at hand and no danger threatened he crept slowly 

 along, peering safely from a narrow crevice between 

 earth and shell, and at the first hint of trouble 

 withdrew within his mineral castle. Such a pro- 

 cedure made for individual safety, but cramped the 



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