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the process not been actually observed to take place, the two 
conditions might have been regarded as belonging to distinct 
organisms. In other parts of the preparation, the mycelial 
threads had resolved themselves into innumerable conidial 
cells, while in others they were more or less completely decom- 
posed into gelatinous masses containing granules and bacteroid 
staves.” 
Several other experiments of a similar kind were made, with 
pretty nearly the same results. The only question which here 
occurs to the author is that concerning the origin of bacteria ; 
but that I think he gets over very fairly. The conclusions 
which he states are as follows : — 1. Specimens of rain-water in 
Calcutta, collected with every precaution to ensure their freedom 
from contact contamination, sooner or later frequently show the 
presence of spores, mycelium, zoospores, monads, bacteroid 
bodies, and distinct bacteria. 2. They do not, as a rule, con- 
tain any of the higher forms of infusoria. 3. The zoospores 
are demonstrably derived from the mycelium arising from com- 
mon atmospheric spores. 4. There is every probability that 
the monads and bacteria have a similar origin, but it remains 
quite uncertain whether their development is due to hetero- 
genesis, or to the presence of their germs within their parent 
cells, or as the result of a process of normal development in the 
latter. 
The next subject examined by Dr. Cunningham is that 
relating to the microscopic character of the air in sewers. 
He placed his aeroscope in such a position that it would have 
an opportunity of examining the air proceeding from the sewage 
of Calcutta, but the results he obtained were not very important 
(see fig. 3, Plate CIX.). He found as a rule nothing but bacteria 
and the spores, most probably, of aspergillus. And both these 
he thus accounts for. The bacteria, he says, are found here 
more readily than in the outer air, because the moisture renders 
them more readily seen ; inasmuch as they change their form 
under the influence of drought, they are less observed in ordi- 
nary preparations. As to the presence of aspergillus, and that 
alone, he thinks it is due to the fact that of course other fungal 
spores could not exist in the sewer atmosphere, while aspergillus 
meets there the damp atmosphere and luxuriant organic matter 
which it requires. 
The other specimens figured in our plate are copies of some 
few of those which Dr. Cunningham has collected by his aero- 
scope, which was exposed for 24 hours each day during the 
months of April, May, and June, 1872, at the Presidency Jail, 
and at a similar locality in Alipore. The results of these 
gatherings are not so strikingly remarkable as we should have 
expected, possibly for a reason that we shall refer to further on; 
