WITH PURE COLLOIDAL SILICA 85 



it seems that the combined effect of the higher 

 temperature and the increased light leads to the 

 appearance of organisms within the tubes in a 

 comparatively short time, so that we can look for- 

 ward with fair certainty to the appearance of 

 living organisms within them in from four to 

 eight weeks the longer period being necessary 

 if the preliminary heating has been as high as 

 135 C., and even then only a sparing number of 

 single Torulge, rather than groups, will probably 

 be met with. 



I have made no high temperature experiments 

 with yellow solutions prepared with this colloidal 

 silica, but expect that such solutions would yield 

 equally satisfactory results, judging from certain 

 tentative trials at 100 C., in which 12-18 drops 

 of the colloidal solution were used, with eight 

 drops of the pernitrate of iron, to the ounce of 

 distilled water. In all the trials with this solution 

 the boiled fluid became of a pale port-wine colour; 

 and, with eighteen drops, a small but distinct 

 amount of sediment was produced. After an ex- 

 posure of three weeks at the south window, with 

 the aid of the centrifuge, plenty of Torulaa and 

 minute Moulds were obtained from the flasks. 



