THE EOZOIC AGES. 25 



the sea, and covering its gelatinous body with a thin 

 crust of carbonate of lime or limestone , adding to this, 

 as it grew in size, crust after crust, attached to each 

 other by numerous partitions, and perforated with 

 pores for the emission of gelatinous filaments. This 

 continued growth of gelatinous animal matter and 

 carbonate of lime went on from age to age, accumu- 

 lating great beds of limestone, in some of which the 

 entire form and most minute structures of the creature 

 are preserved, while in other cases the organisms have 

 been broken up, and the limestones are a mere con- 

 geries of their fragments. It is a remarkable instance 

 of the permanence of fossils, that in these ancient 

 organisms the minutest pores through which the 

 semi-fluid matter of these humble animals passed, 

 have been preserved in the most delicate perfection. 

 The existence of such creatures supposes that of other 

 organisms, probably microscopic plants, on which they 

 could feed. No traces' of these have been observed, 

 though the great quantity of carbon in the beds 

 probably implies the existence of larger seaweeds. 

 No other form of animal has yet been distinctly 

 recognized in the Laurentian limestones, but there are 

 fragments of calcareous matter which may have be- 

 longed to organisms distinct from Eozoon. Of life on 

 the Laurentian land we know nothing, unless the 

 great beds of iron ore already referred to may be 

 taken as a proof of land vegetation.* 



* It is proper to state here that some geologists and natural- 

 ists still doubt the organic nature of Eozoon. Their objections, 



