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No attempt worth mentioning has ever been made to adduce 
evidence of the spontaneous production of living from dead 
matter,, unless it be with reference to low organisms whose 
minuteness almost baffles our means of investigation. Putre- 
fying organic solutions are found to swarm with microscopic 
creatures, whose presence at first sight, and even after a great 
amount of careful investigation, is very difficult to account for 
on the supposition that they came from germs. But if the 
germs, if germs there be, of such creatures bear anything like 
the same proportion in size to the adults that they do in the 
higher animals, one can foresee that a full examination of the 
question must be beset with enormous difficulties. I think 
the immensely preponderating weight of evidence obtained by 
those who have most carefully investigated the question is, 
that if germs are excluded no life is found. 
With respect to the answer to the second question, the 
weight of authority at the present day seems more divided. 
It would ill become me to criticise the labours of those who 
have worked in fields which I have not explored. Yet, looking 
at the thing from the point of view of an outsider, I cannot 
refrain from saying, that it seems to me that speculation as to 
the transmutation of forms has run utterly rampant. A certain 
amount of change yielding sub-permanent varieties no doubt 
presents itself to our observation, as in breeds of cattle and 
races of men, and it is likely enough that the same causes of 
variation operate beyond what we can actually prove. But, 
with all due allowance for such changes, is it conceivable that 
they could bridge over the enormous interval which separates 
the higher animals and man himself from some low organism ? 
I am no biologist, my own studies in natural science having 
lain in the domain of physics. But accustomed as I am to the 
severe demands for demonstration which in the physical 
sciences are made a condition of the acceptance of a theory, 
I confess that it is not without astonishment I have come 
across what seems to me the coolness of assumption with which 
mere speculations are spoken of as if they were established 
truths by many who, following in some respects in the wake 
of the great leaders of biological science, have not had time 
to acquire that vast store of knowledge which puts the mind 
in a condition properly to judge of the weight of evidence by 
which a particular hypothesis may be supported. 
On the whole, while freely acknowledging the operation of 
natural causes, and thinking it probable that they extend 
far beyond the boundaries of our knowledge, and that accord- 
ingly we may seek to include the latest well-established 
scientific theory in some yet higher generalization, I see no 
