98 



THE DAWN OP LIFE. 



It is from a sketcli by Dr. Carpenter^ and shows the 

 delicate canals partly filled with calcite as clear and 



JPiG. 23. Slice of Crystalline Lower Silurian Limestone ; showing 

 Crinoids, Bryozoa, and Corals in fragments. 



m^^S) 



Fig. 24. Wall of Eozoon penetrated with Canals. The unshaded 

 ^portions filled with Calcite. {After Carpenter.) 



colourless as that of the shell itself, and distinguish- 

 able only by careful management of the light. 



In the case of recent and fossil Foraminifers, these 

 — when not so little mineralized that their chambers 



