l/50th 

 mussel 



146 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



The chlorinated sea- water in the first jar was re-dosed so 

 as to make it of concentration 5 per million — the water itself 

 not being changed. This solution was allowed to stand 

 another day. 



Fourth Sampling. After two days in chlorinated sea-water. 

 f Plate 1, 8 red colonies. 

 „ 2, 8 

 „ 3, 4 

 „ 4,10 

 „ 5, 8 

 Mean number of sewage bacteria per mussel = 380. 



The water still being unchanged, fresh chlorine solution 

 was again added so as to bring up the strength to 5 per million. 

 This water, with its contained mussels, was allowed to stand 

 another day. 



Fifth Sampling. After three days in chlorinated sea-water. 

 Plate 1, 2 red colonies. 



>? 2, 2 „ 



Mean number of sewage bacteria per mussel = 116. 



Fifteen mussels had been put into the jar originally. 

 Two of them died. 



It is clear, therefore, that mussels may live, open their 

 shells, and circulate water through the mantle cavity when 

 that water contains 5 parts per million of dissolved chlorine. 

 In such a medium mussels cleanse themselves from ingested 

 sewage bacteria. 



(4) The effect of change of medium on the biological 

 characters of intestinal bacteria. 



It has been suggested that micro-organisms living in the 

 human alimentary canal, and exhibiting certain definite 

 fermentation reactions with certain sugars, might no longer 

 do so when they inhabit a widely different medium, say, 



l/50th 

 mussel 



