420 Spontaneous Generation. [July, 
sealed, and sometimes even then. We therefore keep the ammo- 
nia in a separate solution, mixing them when required. 
A portion of the fine dust of the maceration was now taken 
and thoroughly scattered through the air of the prepared cham- 
er. The condensed beam from an oxyhydrogen lime-light! 
was then sent through it. Its line of passage was far more 
brilliantly marked inside the chamber than in the outer air. It 
was deemed inexpedient to insert the fluids while such brilliant 
points were visible in the air, and four hours were suffered to 
elapse. The lime-light beam was still visible with perfect dis- 
tinctness, but its path within the chamber was much less brilliant 
and more homogeneous than it was without. The fluids were 
then carefully mixed, and five small glass basins of the mixture 
were inserted. The whole was undisturbed for five days. At 
the expiration of that time the beam of the lime-light sent 
through the chamber was absolutely invisible, although perfectly 
clear in the open air on both sides of it. 
The fluids were now withdrawn. Ten “ dips’? were taken out 
of each basin for microscopical examination. Jn every “ dip” 
— that is, fifty in all— one or other.of the monads appeared, and 
were in a state of active fission; and in twenty-seven of the 
“ dips” both monads were found. Bacteria swarmed the field, 
which of course I fully expected. 
I now took five other glass vessels, and inserted them with 
great care into the now moteless air of the chamber, and poured 
in, as before, fresh Cohn’s fluid. They were exposed for another 
five days. On careful microscopical examination of seventy-five 
“dips” not a single monad of either form appeared; bacteria 
were feebly present, but of course no steps were taken to guard 
against these, and, as before, they were anticipated. 
The air of the chamber was again impregnated with dust, a 
before, suffered for a time to settle, and these same vessels of 
fluid, which had yielded negative results, were again placed 10 
the chamber. At the expiration of five days they were aga? 
examined, and one or other of the monads was found in every 
successive “ dip.” 
Now let it be observed that there can be no possible error a3 
to the forms. They were the identical species of the maceration, 
with which I am as familiar as with a barn-door fowl. What, 
' then, is the logic of these facts? Dr. Tyndall proves that bac- 
1 This was of course very much less capable of “searching” than the electric 
beam ; but it served for the rougher end I had in view. ‘ 
