DEVONIAN ERA. 91 



that throng the existing ocean. The life-forms of the pe- 

 riod are, in their kind, neither larger nor smaller, neither 

 less perfect nor less complex, than those of the current era. 

 From the beginning, and simultaneously, species and genera 

 and orders assume their distinctive characters ; there are 

 no transitional forms (in the ordinary sense of the term) 

 through which we can trace the development of the higher 

 from the lower ; each species takes its place from the be- 

 ginning, and varies only within a certain defined limit ; 

 while the whole, obeying the impulses and instincts of life, 

 subserve with unerring certainty the creational functions 

 they were destined to perform. 



We now pass from the Silurian to the Old Red sandstone, 

 or, as it is now more frequently termed, the Devonian 

 epoch. And here, in its sandy and pebbly deposits, we find 

 more decided evidence of frequent alternations of sea and 

 land, of broad shallow bays, and long reaches of shingle- 

 covered shores. Much of the silurian deep sea had been 

 upheaved into dry land ; the former islands and continents 

 had received new configurations and altitudes ; and the 

 seas so changed must have been subject to the influences 

 of other tides and currents. We have also clearer evidence 

 of estuarine and lake areas ; and were this the place to 

 enter on questions of physical geology, testimony is not 

 wanting to prove the existence in certain regions of a cold 

 or glacial climate.'"" All this implies numerous modifications 



* Whoever has examined the bouldery conglomerates of the Scottish 

 Old Red, with their large irregular blocks, their peculiar unassorted 

 aggregation, the nature of the cementing matrix, and the frequent 

 " nestings" or interlaminated patches of fine argillaceous sandstone, 

 must have had suggested to his mind the idea of ice-action. And this 

 notion must have been strengthened when he turned to the sandstones, 

 and found them imbedding angular fragments of rock, shale, and even 

 clay, which could scarcely have suffered transport unless enclosed in 

 drifting ice-floes. The paucity of life in certain areas seems also a further 



