THE DAWN OF LIFE 



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some cases replaced by serpentine in a flocculent 

 form. At the opposite extreme are specimens, or 

 portions of specimens, in which the chambers are 

 obhterated by pressure, or occupied only with 

 calcite. In such cases the general structure is 

 entirely lost to view, and scarcely appears in 

 weathering. It can be detected only by micro- 



FiG. 38. — Pla)i of arrangement of Canals in Lamina of Eozoon. 



scopic examination of slices, in parts where the 

 granular structure or the tubulation of the calcite 

 layers has been preserved. All palaeontologists 

 who have studied silicified fossils in the older 

 rocks are familiar with such appearances. 



It has been alleged by Mobius and others that 

 the canal-systems and tubes present no organic 

 regularity. This difficulty, however, arises solely 

 from imperfect specimens or inattention to the 

 necessary results of slicing any system of ramify- 



