WHAT MAY BE LEARNED FROM EOZOON 149 



ments occur in alternate layers, like the broken corals in some 

 Silurian limestones. 



Finally, on this part of the subject, careful observation of 

 many specimens of Laurentian limestone which present no 

 trace of Eozoon when viewed by the naked eye, and no evi- 

 dence of structure when acted on with acids, are nevertheless 

 organic, and consist of fragments of Eozoon, and possibly of 

 other organisms, not infiltrated with silicates, but only with 

 carbonate of lime, and consequently revealing only obscure 

 indications of their minute structure. I have satisfied myself 

 of this by long and patient investigations, which scarcely admit 

 of any adequate representation, either by words or figures. 



Every worker in those applications of the microscope to 

 geological specimens which have been termed micro-geology, is 

 familiar with the fact that crystalline forces and mechanical 

 movements of material often play the most fantastic tricks with 

 fossilized organic matter. In fossil woods, for example, we 

 often have the tissues disorganized, with radiating crystalliza- 

 tions of calcite and little spherical concretions of quartz, or dis- 

 seminated cubes and grains of pyrite, or little veins filled with 

 sulphate of barium or other minerals. We need not, therefore, 

 be surprised to find that in the venerable rocks containing 

 Eozoon, such things occur in the highly crystalline Laurentian 

 limestones, and even in some still showing the traces of Eozoon. 

 We find many disseminated crystals of magnetite, pyrite, 

 spinel, mica and other minerals, curiously curved prisms of 

 vermicular mica, bundles of aciculi of tremolite and similar 

 substances, veins of calcite and crysotile or fibrous serpentine, 

 which often traverse the best specimens. Where these occur 

 abundantly, we usually find no organic structures remaining, or 

 if they exist, they are in a very defective state of preservation. 

 Even in specimens presentingt he lamination of Eozoon to the 

 naked eye, these crystalline actions have often destroyed the 

 minute structure ; and I fear that some microscopists have 



