REVOLUTION VS, EVOLUTION 
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world. Episode number one in the thrilling serial was a crustal 
movement which crumpled the outer layers of the earth into a 
long line of mountain ranges stretching across what is now Bel- 
gium, Northern France and Southern England. These, the 
Paleozoic Alps’^ of Europe, have long since been worn down 
and washed into the sea, but the roots of the quondam cordillera 
still remain. This crustal crumpling was accompanied by a 
general upward movement of all the continents and a deepening 
of the ocean basins so that shallow seas which had hitherto 
spread out over a large proportion of the continental platforms 
retreated oceanward and left dry land or broad swamps where 
great bays and estuaries had been. It so happens that the 
overwhelming majority of marine organisms are adapted to life 
in the shallow seas alone. The greater part of the deep sea is 
nearly or quite devoid of life ; only in the upper hundred fathoms 
and on the ocean floor are living creatures found. More than 
95 per cent of all the inhabitants of the sea are confined to the 
shallow coastal waters between the strand and the hundred- 
fathom line. Previous to this crustal disturbance, the area of 
this particular zone had been very large and life had expanded 
and multiplied therein. Now, its area was reduced to a small 
fraction of its former extent, and the severity of the struggle for 
existence that must have taken place within this dwindling; 
zone can well be imagined. 
Then followed episode two. Gradually the climate of the 
world changed from its former agreeable warmth to Arctic 
cold. Great ice sheets, far more extensive than those of the 
much later and better known epoch to which the name ^^The 
Great Ice Age’’ is frequently applied, formed upon the lands 
and spread in all directions. In India and in Bolivia these 
glaciers reached even within the tropics, while in South Africa 
and Australia they were only slightly less extensive. The life 
of land and sea, alike, was diastrously affected by these adverse 
climatic conditions, and the end of the Paleozoic Era marks 
also the termination of scores of genera and families and even 
of many orders of animals and plants. 
