DOES SILICON REPLACE CARBON? 115 



ally sealed and subsequently further heated. 

 (See Plate 5, Fig. 29.) 



(d) Then, lastly, there is the fact that the solu- 

 tions contain colloidal silica, and up to the 

 present there is no good evidence that or- 

 ganisms can be engendered in any mere 

 saline solution which does not contain col- 

 loidal silica. 



Taken together, these facts are certainly very 

 suggestive that silicon has replaced carbon, in part 

 at least, in the formation of the protoplasm enter- 

 ing into the constitution of the organisms found 

 within the experimental tubes. Such a supposition 

 seems, indeed, as indicated in Section IX., to sup- 

 ply the only possible reason for the appearance 

 of the organisms within the experimental tubes. 



