OPPONENTS AND OBJECTIONS. 173 



whicli I made in one of my earlier papers on the 

 Laurentian fossils : — 



" This subject opens np several interesting fields of 

 cliemical_, physiological^ and geological inquiry. One 

 of these relates to the conclusions stated by Dr. Hunt 

 as to the probable existence of a large amount of car- 

 bonic acid in the Laurentian atmosphere, and of much 

 carbonate of lime in the seas of that period, and the 

 possible relation of this to the abundance of certain 

 low forms of plants and animals. Another is the com- 

 parison already instituted by Professor Huxley and 

 Dr. Carpenter, between the conditions of the Lauren- 

 tian and those of the deeper parts of the modern ocean. 

 Another is the possible occurrence of other forms of 

 animal life than Eozoon and Annelids, which I have 

 stated in my paper of 1864, after extensive microscopic 

 study of the Laurentian limestones, to be indicated by 

 the occurrence of calcareous fragments, dijSering in 

 structure from Eozoon, but at present of unknown 

 nature. Another is the effort to bridge over, by 

 further discoveries similar to that of the Eozoon Ba- 

 varicum of Giimbel, the gap now existing between the 

 life of the Lower Laurentian and that of the Prim- 

 ordial Silurian or Cambrian period. It is scarcely too 

 much to say that these inquiries open up a new world 

 of thought and investigation, and hold out the hope of 

 bringing us into the presence of the actual origin of 

 organic life on our planet, though this may perhaps be 

 found to have been Prelaurentian. I would here take 

 the opportunity of stating that, in proposing the name 



