WHAT IS EOZOON? 69 



surface. Such creatures may be regarded as tlie 

 simplest and most ready media for the conversion of 

 vegetable matter into animal tissues, and their functions 

 are almost entirely limited to those of nutrition. Hence 

 it is likely that they will be able to appear in the most 

 gigantic forms under such conditions as afford them 

 the greatest amount of pabulum for the nourishment 

 of their soft parts and for their skeletons. There is 

 reason to believe, for example, that the occurrence, both 

 in the chalk and the deep-sea mud, of immense quantities 

 of the minute bodies known as Coccoliths along with 

 Foraminifera, is not accidental. The Coccoliths appear 

 to be grains of calcareous matter formed in minute 

 plants adapted to a deep-sea habitat ; and these, along 

 with the vegetable and animal debris constantly being 

 derived from the death of the living things at the sur- 

 face, afford the material both of sarcode and shell. 

 Now if the Laurentian graphite represents an exuber- 

 ance of vegetable growth in those old seas proportionate 

 to the great supplies of carbonic acid in the atmosphere 

 and in the waters, and if the Eozoic ocean was even 

 better supplied with carbonate of lime than those 

 Silurian seas whose vast limestones bear testimony to 

 their richness in such material, we can easily imagine 

 that the conditions may have been more favourable to 

 a creature like Eozoon than those of any other period 

 of geological time. 



Growing, as Eozoon did, on the floor of the ocean, and 

 covering wide patches with more or less irregular 

 masses, it must have thrown up from its whole surface 



