APPENDIX 305 



and having the walls of its cells thickened by a 

 supplemental tubulated deposit like that of Calcar- 

 ina, would approach very near to Eozoon. 



The question of the general relation of an organ- 

 ism like Eozoon to creatures known to us in the 

 modern seas may be answered in either of two 

 ways: — (i) Functionally or in relation to the posi- 

 tion of such an animal in nature : or (2) Zoologi- 

 cally, or with reference to its affinities to other 

 animals. With reference to the first consideration, 

 the answer is plain. The geological function of 

 Eozoon was that of a collector of calcareous matter 

 from the surrounding waters, then probably very 

 rich in calcium carbonate, and its role was the same 

 with that of the Stromatoporae and calcareous 

 Sponges, smaller Foraminifera and Corals in latter 

 times. The answer to the second aspect of the 

 question is less easy. An ordinary observer would 

 at once place Eozoon with the Stromatoporida^ or 

 Layer-corals, which fill or even constitute whole 

 beds of limestone in the- Cambro-Silurian, Silurian 

 and Devonian Periods. While, however, Eozoon 

 has been claimed on the highest authority for the 

 Rhizopods, the Stromatoporae and their allies have 

 been regarded as Sponges, or more recently as 



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