154 



THE DAWN OP LIFE. 



chambers communicating with one another (figs. 40 

 and 41 A). Above this where the cup expands, its walls 

 are composed of thin outer and inner plates,, perforated 

 with innumerable holes, and connected with each other 

 by vertical plates, which are also perforated with round 

 pores, establishing a communication between the radia- 

 ting chambers into which they divide the thickness 



a _____ 



-^ - T " "ir'-'^^xi^i ^ 



I 

 FIG. 41. Structures of Archceocyathus Profundus. 



(a.) Lower acervuline portion. (&.) Upper portion, with, three of the radiating 

 laminae, (c.) Portion of lamina with pores and thickened part with canals. 

 In figs, a and b the calcareous part is unshaded. 



of the wall (figs. 38, 39, and 41 B). In such a struc- 

 ture the chambers in the wall of the cup and the 

 irregular chambers of the base would be filled with 

 gelatinous animal matter, and the pseudopods would 

 project from the numerous pores in the inner and 

 outer wall. In the older parts of the skeleton, the 



