348 FOOT-NOTES TO EVOLUTION. 
But can we give them belief? Let us pass by the 
doctrine of monism, with which science can not concern 
itself. What of the corollaries? Spon- 
taneous generation, for example, has 
been the basis of many experiments. 
Like the transmutation of metals, it 
seems reasonable to philosophy. The one idea has 
been the will-o’-the-wisp of biology as the other has 
of chemistry. We know absolutely nothing of how, if 
ever, non-life becomes life. So far as we know, genera- 
tion from first to last has been one unbroken series—all 
life from life. We have no reason to believe that spon- 
taneous generation exists under any conditions we have 
ever known. We have likewise reason to believe that if 
it exists at all we have no way of recognising it. The 
organisms we know have all had a long history. Even 
the simplest ever examined shows traces of a long an- 
cestry, a long process of natural selection, and of many 
concessions to environment. We know of no life that 
does not show such concessions. We know no creature 
that does not show homologies with all other living be- 
ings whatsoever. So far as this fact goes, it tends to 
show that all life comes from one common stock, a single 
generation or creation. If this be true, spontaneous 
generation, whatever it may be, is not a phenomenon of 
frequent occurrence. 
If life does now appear without living parentage, if 
organisms fresh from the mint of creation are now devel- 
oped from inorganic matter, they are so simple that we 
can not know them. They are so small that we can not 
find them. They would be made, we may suppose, each 
of a small number of molecules. If there is truth in the 
calculations of Lord Kelvin and others, that a molecule 
in a drop of water is as small as a marble in comparison 
with the earth, then we may not look for these creatures, 
Spontaneous 
generation not 
science. 
