68 EVOLUTION AND THE 
induction be founded but on a single instance.” Now 
here, far from being based upon a single instance, the 
fact that very many different kinds of living matter 
are killed by a temperature of 140° F., rests upon the 
repeatedly recorded observations of several indepen- 
dent investigators—upon the observations of Pouchet, 
Liebig, Cantoni, Hoppe-Seyler, Kiihne, Max Schultze, 
myself, and others. 
But as it is the fact that living matter is killed at 
140° F., and as it is also true that certain fluids heated 
to much higher temperatures (to 212° F. and upwards) 
and subsequently exposed to certain conditions free 
from all possibility of contamination with living 
matter, will shortly swarm with the living things 
whose mode of origin we desire to learn, the man 
of science is compelled to conclude that such living 
Organisms must have originated independently of 
living germs, and, therefore, after the manner of 
Crystals. Here then is our ‘crucial instance.’ 
Thus by this simple resort to the ‘Method of 
Difference,’ we are enabled to solve our problem, and 
finally decide between two rival hypotheses. The 
occurrence of Archebiosis is, therefore, established as 
a natural phenomenon, and like other natural pheno- 
mena, we are entitled to believe not only that it will 
recur whenever the conditions are similar or otherwise 
suitable, but that it has been in operation through 
