1864. | Samunxson on the Source of Living Organisms. 609 
numbers in pure distilled water, that I had ample opportunities to 
verify and sketch it under the microscope. 
X 640 d78 x.900 qT 
Fic. 6.—Ameba Balbianii, found by me in pure distilled water, 
My figures are more highly magnified than Dr. Balbiani’s; but an 
inspection of the Plate, and a comparison with my colleague’s figures, 
will exhibit the identity. 
Lastly, Dr. Balbiani found in his infusions, both animal and 
vegetable, a little ciliated type, Cyclidium glaucoma, and wrote to me 
some time afterwards that he had found the same form in moistened 
dust wiped from his window. He sent me a drawing, which it is, 
however, unnecessary to append. Here, then, we have characteristic 
types representing three distinct groups of Protozoa which have been 
observed at the same time in infusions of various kinds, and then the 
identical types subsequently traced to the atmosphere itself, or to the 
dust which it holds in suspension. 
But the objection, refined as it may be, might not improbably be 
raised by the advocates of heterogenesis against these experiments, 
that perhaps the infusoria which I have thus traced in pure distilled 
water are spontaneously produced from the particles of organie sub- 
stances which find their way along with dust into the vessel containing 
the water. 
It is, therefore, advisable to meet this difficulty beforehand, and I 
can best do so by repeating here an account of one of my experiments, 
described last year before the members of the British Association.* 
I had exposed (July, 1863,) some pure distilled water in a glass vessel, 
placed in a box covered with a glass lid, which was left partially open, 
and after a few days could trace scarcely any appearance of life in the 
water, inasmuch as the glass cover had intercepted the dust to such a 
degree as to have become to some extent opaque through the deposit. 
I therefore removed the dust from the glass lid into the contained 
vessel, by washing it with a littlé distilled water, and then left it fully 
exposed to the atmosphere. 
The very next day I re-examined the vessel of distilled water. 
When exposed on the previous day, the dust had clouded it a little, 
but now it had settled at the bottom as a fine film or deposit. On 
pouring off the water carefully, and examining this deposit as it lay 
in the vessel with a low power (about 75 diameters), it appeared to 
consist of a number of minute siliceous fragments, interspersed with 
* Sub-Section D. “ Life in the Atmosphere.” 
