502 Proceedings of the Royal Society 
results obtained need not disappoint the most sanguine investigator. 
Professor Lister has obtained proof that Bacteria are, at all events 
in some cases, directly derived from fungi, of which they are merely 
a special development. He has been able to determine, within not 
very wide limits, the number of individual germs contained in a 
drop of water, and to show that this number is greater in warm 
than in cold weather, and has proved that the number of distinct 
species of microscopic fungi is great beyond all previous imagina- 
tion. There is one special result to which I cannot omit a reference. 
It is, that there are certain fungi which, although rare, and, we may 
therefore conclude, not, under ordinary conditions, hardy, still 
flourish luxuriantly and increase rapidly under certain special con- 
ditions. Thus the fungus which causes the lactic fermentation of 
sugar, is scarcely to be found anywhere but in dairies. Boiled milk 
or perfectly pure milk, may be exposed to air anywhere else with- 
out undergoing the lactic fermentation; other fungi, producing 
different effects, will grow in it; but if milk be exposed in a dairy, 
this particular fungus overcomes all others, and the lactic fermen- 
tation alone takes place. Milk is the soil specially suited for its 
growth, but it does not appear there of itself — it must be introduced 
from without. 
II. Another matter of great interest connected with Mr Lister’s 
work, is the means which it will no doubt put into our hands of 
preparing many chemical substances. Although he has not fully 
investigated the various chemical changes which accompany the 
growth of microscopic fungi, he has shown that each species pro- 
duces its own effect; and as he has taught us how to obtain speci- 
mens of each species without mixture of any other, he has put it 
in our power to produce specific fermentations, and study them un- 
disturbed by the presence of other kinds of fermentation. 
III. But more general interest attaches to Mr Lister’s paper as a 
very important step in the settlement of the question : Does life 
ever arise from lifeless matter, or is the origin of life not as great 
a mystery and as far removed from the grasp of our scientific 
methods as the origin of matter itself? If living things never 
develope out of dead nature in the ordinary processes of nature, 
we are forced to the conclusion that they either have existed 
always, or have been miraculously created. It has been sup- 
