206 STUDIES IN THE EVOLUTION OF ANIMALS 



photosphere of the sun are no other than pure incandescent carbon. 

 Owing to the intense heat, the carbon is dissevered from all its 

 possible combinations and shines and radiates heat as the coal in 

 our grate does, or as the carbon filament in the electric lamp does. 



It is logical therefore to infer that our earth had, at one time, 

 a vast deal of this same material in its atmosphere. Then, as it 

 cooled down, the carbon began again to combine with oxygen l to 

 form CO 2 . If this be so, it would follow that at one time our 

 atmosphere was choked with CO 2 , and all life, as we now know it, 

 must have been impossible till the evolution of low forms of plants 

 undertook to liberate the oxygen and hoard up the carbon in the 

 plant tissues. 



Now a large quantity of CO 2 in the air would also mean a 

 large quantity of CO 2 absorbed by the water. And this again 

 would mean a large quantity of carbonate of lime in solution in the 

 water. Hence we find all the lower forms of primitive life, even 

 down to seaweeds, mostly encased in calcareous material, forming 

 more or less thick shells of innumerable forms, carapaces, exo- 

 skeletons, etc. 



It is only necessary to think of the chalk and other limestone 

 rocks, which are formed of countless myriads of foraminiferous 

 shells, and of the coral rocks, to have some idea of the vast amount 

 of carbonate of lime which has been withdrawn from the waters of 

 our earth ; for these minute animals and corals could have got 

 the lime they needed only from the lime salts in solution in water. 

 Moreover, the fauna of the seas could obtain the materials of both 

 their inner and outer skeletons only from the same source. 



The abstraction of carbon from the atmosphere, and the hoard- 

 ing of it in coal measures, and the abstraction of the same carbon, 

 in the shape of carbonate of lime, from the waters, and the hoarding 



1 Oxygen may not have been detected in the sun, but we have it in our atmosphere. 



