84 



ORGANIC DEPENDENCE AND DISEASE 



tivities, an unsolved problem. This activity of course plays 

 a large part in the scavenging process which helps to clean 



up the organic excesses 

 and restore the inor- 

 ganic balance of nature. 

 If algae can cause the 

 deposition or secretion 

 of lime carbonate, as 

 they began to do on a 

 vast scale even in Pre- 

 cambrian times, and do 

 this in effect by extract- 

 ing the excess molecule 

 of carbon dioxide from 

 waters carrying lime 

 carbonate in solution, 

 it seems reasonable to 

 believe that in the same 

 early ages algae might 

 also have been the in- 

 struments of lime solu- 

 tion by virtue of the 

 excessive atmosphere of 

 carbon dioxide which 

 they of necessity car- 

 ried about them. Gener- 

 ally estimated we must 

 ascribe to these plant 

 parasites an early adap- 

 tation and an increas- 

 ing activity which seems 



Fig. 68. Perforating algae Hayeia Jtematitica to be in fair Correspond- 



in the shell of the brachiopod Lingula. From ence With the increase 



the iron beds of the Wabana series (Ordovi- . r , ,, -, . 



cian). Conception Bay, Newfoundland. m ^-shelled inverte- 



. x no. 6. x 100. (A. o. Hayes, op. dt.) brates. Unknown hith- 



