PRE ac E, 
SINCE the publication of my larger work, “The 
Beginnings of Life,” in 1872, some long-overhang- 
ing clouds have been dispersed. Well-informed men 
of science no longer doubt that swarms of Bacteria 
can be made to appear within sealed glass vessels 
containing suitable fluids, after the vessels and their 
contents have been exposed to the temperature of 
boiling water. The thorough establishment of this 
fact has been of the greatest importance. 
Statements as to the reality of so unexpected 
an appearance of Bacteria were previously received 
with actual disbelief or the profoundest scepticism. 
It was much easier to imagine that I had been 
mistaken or deceived than to suppose that living 
Bacteria could really appear within closed flasks 
which had been subjected to the conditions men- 
