312 PROCEEDINGS OF SOCIETIES. 
then sifted them through muslin on the surface of distilled 
water, each kind having, of course, its appropriate vessel of 
water. He also exposed pure distilled water in a three- 
partitioned box covered with lids of blue, red, and yellow 
lass. 
: The results of these experiments he read before the 
Academy of Sciences in July, and in the same month he re- 
peated them, which were concluded just before the meeting 
of the Association. 
The following are the results obtained from this double set 
of experiments : 
In the case of the distilled water, exposed under co- 
loured-glass lids (partially open), the glass intercepted the 
dust, and there was hardly any sign of life. When the dust 
was washed into the distilled water, a light deposit settled at 
the bottom of the vessels, and on examination under a low 
power the subsequent day, the author found mineral particles 
imbedded in a gelatinous film. (He examined the deposit 
without removing it from the vessel, by pouring off the water 
and placing the glass vessel itself under his instrument.) 
This film, under a higher power, was resolved into a mass of 
minute, fixed monads, possessing a tremulous motion. The 
next day a re-examination showed that these monads had be- 
come active, and peopled the water. 
So much for the distilled water only. Now as regards the 
various kinds of dust. 
In that of Egypt, Japan, Melbourne, and Trieste, life was 
the most abundant, and the development of the different 
forms was very rapid. These consisted of Protophytes, Rhi- 
zopoda, and true Infusoria. 
In most of the vessels he first observed the forms known as 
Monads and Vibrions; and from these he traced the develop- 
ment, first of one, and then of another species of Infusoria. 
In the dust of Egypt he found a new Ameeba, whose motions 
were very rapid, and the pseudopodia of which he compared, 
both as regards their shape and mode of formation, to the 
soap-bubbles blown by children with a pipe. He described 
the normal globular form of this Ameeba, its gradual changes 
until its pseudopodia were in full action, its conjugation, and 
some other phenomena in its life-history. 
In the same dust, and in this only, he clearly traced the 
development of Protococcus viridis, which was, at last, 
present in such numbers as to tinge the water green. 
In Egypt, Melbourne, and Trieste, he found Cercomonas 
acuminata (Dujardin), which his colleague and he had found 
in the dust of Paris and Liverpool ; and in Egypt he followed 
