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boiling destroys all germs, or that because no germs can be dis- 
covered with the highest powers none exist. There are no data 
by which any limit can be assigned to the minuteness of creatures 
that may possess a complex organisation, unless indeed mathe- 
maticians concerning themselves with molecular physics compute 
it at something far beyond our possibilities of vision. Probably 
the minutest of known forms does at some period of its life- 
history resort to sexual generation, as Claude Bernard supposes. 
The question will arise, how do such facts, and suppositions 
drawn as inferences from them, accord with theories of abio- 
genesis , which is a less perplexing term than spontaneous 
generation. Abiogenesis supposes that, under certain conditions, 
matter not derived by descent from previously living matter, 
can set up vital processes and grow. The opponents of this 
theory accept in a broad sense the old Harveian doctrine omne 
mvum ex ovo , and believe that no inorganic matter becomes 
organic except under the directing force of a germ that had a 
living parent. Under any hypothesis we must admit the pro- 
bable existence of germs we cannot see, perhaps some so small 
that our eyes can never behold them, as they may be beyond 
the limits any optical aid we may obtain can reach. "We have 
also no reason for supposing that a heat of 300° necessarily de- 
stroys all germs, and if all are killed at a higher one the abio- 
genist would still need, for the complete working of his theory, 
to suppose that no possible heat could prevent inorganic matter, 
under certain conditions, from becoming organic. Doctrines of 
evolution, beginning with a nebulous condition of our own and 
of other globes, require us to imagine that life existed poten- 
tially, if not actually, through the fiery stages of condensation 
when the earth was a surging molten mass, or that it was intro- 
duced from without when the cooling had proceeded far enough. 
Most believers in development doctrines would probably prefer 
the first of these suppositions, and expect that, by further 
advances of science, connecting links and steps of transition will 
be found between inorganic and organic matter — between non- 
living and living substance. There is an evident convergence 
of all sciences from physics to chemistry and physiology towards 
some doctrine of evolution and development, of which the facts 
of Darwinism will form a part ; but what ultimate aspect this 
doctrine will take there is little if any evidence to show, and per- 
haps it will not be shaped by the human mind until metaphysical 
as well as physical inquiries are much more advanced. If, on 
the one hand, there are thinkers who try to materialise all that 
others call spiritual, there are philosophers who, so to speak, 
spiritualise matter, and expect matter and spirit to prove oppo- 
site sides of the same thing. 
Darwin’s remarkable speculative guess of pangenesis is still 
