OF CREATION. 



29 



Fig. 2 



not very probable, that our atmosphere at its first 

 formation contained a larger supply of carbonic acid 

 gas than at present ; but such an assumption is not 

 at all necessary to account for the first secretion of 

 carbonate of lime required to form the habitations 

 and the skeletons of the original inhabitants of our 

 globe. 



Among the most simply organized 

 of the silurian species, and amongst 

 those found in the beds of oldest 

 date, are the fossils called Grapto- 

 lites, which seem to have been the 

 horny skeletons of animals not un- 

 like those which are often met with 

 on the coral and sea-weeds of our 

 own coast. They were formed, like 

 these, by a vast multitude of indi- 

 vidual polyps attached to a tough 

 central mass, the whole constituting 

 a kind of compound animal, in which 

 each individual works to increase the 

 general mass, and is affected by that 

 which affects this mass ; but each, 

 also, has a separate existence, being 

 provided with a stomach and arms, 

 to obtain and digest food, and capa- 

 ble of being injured or destroyed without the func- 

 tions of the complete body being at all interfered with. 



Polyps, as animals of this low organization are 

 called, appear to have been among the first of created 

 beings, and are also those which have been changed 

 least since the period of their original introduction up 

 to the present time. Their extreme simplicity of 



SERTULARIAN 

 CORALLINE. 

 (Graptolite.) 



