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THE DAWN OF LIFE. 



the mass, as fibres of oxide of iron or manganese liave 

 grown in the silica of moss-agate ; but this theory 

 would be encompassed with nearly as great mechanical 

 and chemical difficulties. The only rational view that 

 any one can take of the process is, that the calcareous 

 matter was the original substance, and that it had 

 delicate tubes traversing it which became injected with 

 serpentine. The same explanation, and no other, will 

 suffice for those delicate cell- walls, penetrated by in- 

 numerable threads of serpentine, which must have been 

 injected into pores. It is true that there are in some 

 of the specimens cracks filled with fibrous serpentine or 



Fig. 27. Diagram showing the different appearances of the cell-wall 

 , of Eozoon and of a vein of Chrysotile, when highly magnified. 



chrysotile, but these traverse the mass in irregular 

 directions, and they consist of closely packed angular 

 prisms, instead of a matrix of limestone penetrated by 

 cylindrical threads of serpentine. (Fig. 27.) Here I 

 must once for all protest against the tendency of some 

 opponents of Eozoon to confound these structures and 

 the canal system of Eozoon with the acicular crystals, 

 and dendritic or coralloidal forms, observed in some 

 minerals. It is easy to make such comparisons appear 

 plausible to the uninitiated, but practised observers 

 cannot be so deceived, the differences are too marked 



