450 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



than any Lancashire or Welsh mussels, with the exception 

 of a sample which I report on later on — one taken from 

 the Richie Channel in the full flow of the polluted water 

 containing the sewage of Preston, Southport (probably), 

 Lytham and other towns. The counts of sewage bacteria 

 in the mussels are practically the same in both cases, 

 about 20,000 organisms per mussel. But the pollution 

 at Aberdovey is far more significant, potentially more 

 dangerous one may say, than in the case of the Ribble. 

 In the latter estuary the contamination is remote, and 

 it may be the case (I propose to discuss this question in 

 a later report) that a lengthy sojourn of these bacteria 

 in sea water may have changed their character. But in 

 the case of Aberdovey the mussels may be taken from 

 almost the immediate vicinity of a sewer outfall, so that 

 the contamination is almost an immediate one, and only 

 a very short time may elapse between the discharge of 

 the sewage and its ingestion by the shellfish. In these 

 circumstances the same degree of bacteriological 

 pollution is more serious. 



The bacteriological contamination of the mussels 

 taken from the channel at Penhelyg is practically the 

 same as that of the mussels collected from near the sewer 

 outfall. The former ground is only one-half mile distant 

 from the sewer. Now if the discharge of the sewage is 

 regulated as is indicated above, and if the currents in 

 the estuary are as stated, it is difficult to see how these 

 mussels can be contaminated. Yet the contamination in 

 June last was very notable, and we can only conclude 

 that the direction of drift of surface water may at times 

 be such that the sewage flows along the northern side of 

 the estuary towards Penhelyg. It is also possible that 

 sewage may flow from the outfall at other times than for 

 one half-hour at half-flood tide — at any rate, the pos- 



