114 THE ORIGIN OF LIFE 



(a) The freedom with which moulds grow on 

 the surface or in solutions of colloidal silica, 

 as originally recorded by Slack and Chan- 

 dler Roberts, 1 and the fact that green 

 organisms, such as chlorococcus and its 

 allies, when introduced into either of my 

 early solutions, were found to grow and 

 multiply, and that quite as freely in the 

 colourless as in the yellow solution. 1 



(fc) The fact that in my experiments the organ- 

 isms have been invariably found away from 

 contact with the air; never in the strata 

 of water intervening between the deposited 

 silica and the air; but always in and upon 

 the deposited silica or at the bottom of the 

 tubes. 



(c) The fact that the same kinds of organisms 

 have appeared, and also in similar situa- 

 tions, in experiments with the colourless 

 solution in which the air has been expelled 

 by boiling, before the tubes were hermetic- 



1 Quart. Jrnl. of Micros. Science, 1868, pp. 105-108. 



1 The latter fact could not have been easily explained had it 

 not been made known by Willstatter (Liebig's Annalen, 350, 48, 

 1906) that magnesium, and not iron, is the active principle of 

 chlorophyll. Magnesium, I am told, would probably have been 

 present owing to its having been dissolved out of the soft glass 

 by the boiling solutions. 



