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are carried, no doubt, by the sewer gases or currents of air, 
and whenever they find favourable conditions produce the 
disease. The same effect is produced when impure water 
is used for drinking, and this again is an argument in 
favour of the germ theory, as it is never contended that the 
danger is from any gases in the water. 
It is most desirable that these rival theories should be 
carefully examined, as the inodes of getting rid of the 
danger will necessarily differ widely, whichever theory be 
accepted ; if it be the germ theory, then water-trapped 
drains would prevent the escape of most, if not all, the 
germs, but pipes to ventilate the sewers would only diffuse 
and spread the mischief. 
February 26th, 1872. 
Joseph Baxendell, F.R.A.S., in the Chair. 
Mr. Mark Stirrup exhibited sections of shells of mollusca, 
showing so-called fungoid growths. 
He referred to Dr. Carpenter’s report on shell structure, 
presented to the meeting of the British Association, in 1844, 
in which especial mention is made of a tubular structure in 
certain shells, and he cites the Anomia as a characteristic 
example. In the last edition of “ The Microscope,” Dr. 
Carpenter withdraws his former explanation of this structure, 
and now refers it to the parasitic action of a fungus. Mr. 
Stirrup showed sections of this shell penetrated by tubuli 
from the outer to the inner layers of the shell, and it is upon 
the inner layer that the curious appearance of sporangia, 
with slightly branched filamentous processes proceeding 
from them present themselves. 
The parasitic view is strengthened by the fact that these 
markings are not found on all parts of the shell, and are 
certainly accidental. 
