152 THE STORY OF THE EAETH AND MAN. 



of the fishes ; so that, like some modern creatures of 

 their class, they stood, as to respiration, on two stools, 

 and seemed unwilling altogether to commit them- 

 selves to the new mode of life in the uncongenial ele- 

 ment of air. Even the larger and more lizard-like of 

 the coal reptiles may though this we do not certainly 

 know, and in some cases there are reasons for doubting 

 it have passed the earliest stage of their lives in the 

 water as gilled tadpoles, in the manner of our modern 

 frogs. Thus at the very point where one of the 

 greatest advances of animal life has its origin, we 

 have no sudden stop, but an inclined plane ; and yet, 

 as I have elsewhere endeavoured to show by argu- 

 ments which cannot be repeated here,* we have not a 

 shadow of reason to conclude that, in the coal period, 

 fishes were transmuted into reptiles. 



But the reader may be wearied with our long 

 sojourn in the pestilential atmosphere of the coal 

 swamps, and in the company of their low-browed and 

 squalid inhabitants. Let us turn for a little to the 

 sea, and notice the animal life of the great coral reefs 

 and shell beds preserved for us in the Carboniferous 

 limestone. Before doing so, one point merits atten- 

 tion. The coal formation for the first time distinctly 

 presents to us the now familiar differences in the 

 inhabitants of the open sea and those of creeks, estu- 

 aries and lakes. Such distinctions are unknown to 

 us in the Silurian. There all is sea. They begin to 



* " Air -breathers of the Coal Period," p. 77. 



