THE PROGRESS OF LIFE 51 



igneous origin, and probably represents the more or 

 less altered remains of the original crust of the earth. 

 The upper formation consists of limestones and clastic 

 rocks, evidently of aqueous origin, which are called 

 the Grenville and Hastings series. The argillaceous 

 beds interstratified with the limestones have been 

 changed into a rock, which is also called gneiss, 

 although different in chemical composition from the 

 fundamental gneiss. The Grenville series is supposed 

 by Messrs Adams and Barlow, of the Geological Survey 

 of Canada, 1 to have been deposited at a time when the 

 fundamental gneiss, which formed the bed of the ocean, 

 was in a semi-molten or plastic condition, and the 

 sediments sank down into the gneiss, so that in places 

 they were entirely enwrapped by it. It is in this 

 Grenville series that the structure called Eozoon 

 canadense has been found. 



It was the macroscopic characters of Eozoon the 

 regular concentric layers of which it is generally com- 

 posed which first gave rise to the idea that it was of 

 organic origin. But these regular layers are sometimes 

 very few in number, the greater part of the supposed 

 organism being quite irregular in structure ; indeed 

 some specimens are without any arrangement at all 

 and have been called Archceospherince, under the idea 

 that they belonged to a different genus to Eozoon. In 

 its microscopic appearance Eozoon must closely re- 

 semble some of the Foraminifera, or it could not have 

 deceived such experienced observers as Dr Carpenter 

 and Professor Rupert Jones. However, Mr H. J. 

 Carter and Professor Mobius never allowed that Eozoon 

 was organic ; and Professor Zittel, although at first 



1 American Journal of Science and Art, Ser. 4, vol. iii. p. 173. 



