137 



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 modes 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.RA.S., in the Chair. 



Mr. Mark Stirrup exhibited sections of shells of moUusca, 

 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 A7iomia 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 «ections 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. 



