244 THE EVOLUTION OF LIFE 
the case with ten drops of the dilute phosphoric acid 
and ten drops of the iron solution ; but the drops of 
the sodium silicate mixture were smaller, so that ten 
of them only equalled seven minims of water. The 
different ingredients, whether solid or liquid, were 
added to freshly distilled water, and the experimental 
vessels were then at once charged, sealed, and heated 
to this or that temperature. When cool, the tubes 
were exposed either to diffuse daylight or to a 
temperature of about 95 F. in an incubator: for 
varying periods ; and always for weeks or months 
rather than for days. 
Exanination of the Flurds. 
In all the cases in which sodium silicate enters 
into the composition of the experimental fluids there 
is a more or less abundant deposit, such as is shown 
in the experimental tube represented in Fig. 12; but 
even after weeks or months have elapsed there is 
absolutely nothing to show to the naked eye, or to 
the naked eye aided by a good pocket lens, whether 
the tube does or does not contain living organisms. 
In the case of an organic infusion, if organisms 
appear, the fluid in the course of a few days 
becomes cloudy or actually turbid, owing to their 
rapid growth and multiplication ; or if that does not 
occur (as when the fluid has been much superheated, 
and what I have termed! a ‘‘smouldering fermenta- 
tion” is all that is set up) a small amount of sediment 
gradually collects where none previously existed. 
1 Journal of the Linnean Soctety, No. 73 |Zool.], p. 3. 
