73 THE STORY OP TIIE EARTH AND MAM. 



not have provided for. These new forms require the 

 intervention of a higher power, capable of correlating 

 the physical and organic conditions of one period with 

 those of succeeding periods. Whatever powers may 

 be attributed to natural selection or to any other con- 

 ceivable cause of merely genetic evolution, surely pro- 

 phetic gifts cannot be claimed for it ; and the life of all 

 these geological periods is full of mute prophecies to 

 be read only in the light of subsequent fulfilments. 



The fishes of the Upper Silurian are such a 

 prophecy. They can claim no parentage in the older 

 rocks, and they appear at once as kings of their class. 

 With reference to the Silurian itself, they are of little 

 consequence ; and in the midst of its gigantic forms 

 of invertebrate life they seem almost misplaced. But 

 they predict the coining Devonian, and that long and 

 varied reign of vertebrate life which culminates in man 

 himself. No such prophetic ideas are represented by 

 tho giant crustaceans and cuttle-fishes and swarming 

 graptolites. They had already attained their maxi- 

 mum, and were destined to a speedy and final grave in 

 the Silurian, or to be perpetuated only in decaying 

 families whose poverty is rendered more conspicuous 

 by the contrast with the better days gone by. The 

 law of creation provided for new types, and at once for 

 the elevation and degradation of them when introduced; 

 and all this with reference to the physical conditions 

 not of the present only but of the future. Such facts, 

 which cannot be ignored save by the wilfully blind, are 

 beyond the reach of any merely material philosophy. 



