THE LONG ROAD 



times there was a gigantic dragon-fly, measuring 

 more than two feet in the expanse of wings. Still 

 earlier, there were gigantic moUusks and sea scor- 

 pions, a cephalopod larger than a man; then gigan- 

 tic fishes and amphibians and reptiles, followed by 

 enormous mammals. But the geologic record shows 

 that these huge forms did not continue. The mol- 

 lusks that last unchanged through millions of years 

 are the clam and the oyster of our day. The huge 

 mosses and tree-ferns are gone, and only their 

 humbler types remain. Among men giants are 

 short-lived. 



On the other hand, the steady increase in size of 

 certain other species of animals during the later geo- 

 logic ages is a curious and interesting fact. The first 

 progenitors of the elephant that have been found 

 show a small animal that steadily grew through the 

 ages till the animal as we now find it is reached. 

 Among the invertebrates this same progressive in- 

 crease in size has been noted, a small shell in 

 the Devonian becoming enormous in the Triassic. 

 Certain species of sharks of medium size in the 

 lower Eocene continue to increase till they attain 

 the astounding dimensions in the Miocene and Plio- 

 cene of over one hundred feet long. A certain fish 

 appearing in the Devonian as a small fish of seven 

 centimetres in length, becomes in the Carboniferous 

 era a creature twenty-seven centimetres in length. 

 Among the mammals of Tertiary times this same 



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