A Sterile Putreseihle Fluid. By W. H. Dallinger. 291 
through it unseen, although its intensity was incomparably 
diminished. 
The chamber was now entirely left for four days more, and 
then the first six vessels were taken out and examined. Fifteen 
drops were taken from each basin ; five from different parts of the 
surface, five from the middle of the fluid, and five from near the 
bottom. In every drop from every vessel the ealycine monad ap- 
peared, in full vigour, while the " springing monad " appeared in 
every vessel, but only in, on the average, ten drops out of fifteen 
from each. Thus the two monads contained in the infusion were 
developed in the Cohn's fluid from the minute particles of its solid 
debris scattered in the air, and made manifest by the beam. 
Two days after, the other four vessels were examined in pre- 
cisely the same way. But now, although thirty drops were taken 
out of each vessel and thoroughly searched, the ealycine monad 
was wholly wanting in three of them ; and only very feebly mani- 
fested itself in the fourth, being found only in four out of thirty of 
the drops taken. But the " springing monad," although not 
largely present, was found in each vessel, and in ninety-two out of 
a hundred and twenty drops. 
At first this was extremely puzzling. But on reflection, it 
occurred to me that both the actual and the specific weight of the 
germs would influence the length of time taken in descending 
through the air, and the " ealycine monad " was at once the largest 
form, and produced the largest germs of any of those studied. 
^ The ealycine is from the 900th to the TxrVir of an inch in long 
diameter,* whilst the " springing monad " is only the ^gVtr of an 
inch in length.t Here, then, was a probable explanation. The 
heavier germs of the larger monad had nearly all fallen before the 
expiration of the two days, when the covered cups were opened. 
The lighter germs, still lingering in the air, remained in sufficient 
abundance to produce the result detailed. This at least seemed an 
extremely probable explanation, and fortunately the means of 
testing it were at hand. 
The smallest monad in all the series studied by my colleague 
and myself, was only the -^woo to the ^^Vir of an inch in length. 
This pours out from its sac, spore so small, as at first, to be 
invisible, separately, to our best powers.^ I had an infusion some 
twelve months old, in which this form (the " uniflagellate monad ") 
was very largely developed. Indeed there was nothing noticeable 
in it, but this form, and several kinds of bacteria with leptothrix, 
&c. I dried this infusion in the manner before described. The 
dried cake was much more homogeneous, but was still in several 
* ' M. M. J.' vol. xiii. p. 191. t Ibid. vol. x. p. 245. 
X Ibid. vol. xi. pp. 69-71. 
VOL. XVI. Y 
