SEA-FISHERIES LABORATORY. 137 



Second Sampling. Relaid for 4 tides. 



Plate 1, 16 red colonies, white colonies. 



>> 2, 28 „ „ „ 



33 d> ^O 33 2 33 33 



Mean number of sewage bacteria per mussel = 1,150. 

 Third Sampling. Relaid for 6 tides. 



Plate 1, 3 red colonies, no colourless colonies. 

 33 2, 12 ,, ,, ,, 



33 ^3 12 ,, ,, ,, 



Mean number of sewage bacteria per mussel = 450. 



This experiment is exceptional in that no reduction was 

 experienced after 1 day's relaying. Most of the sewage 

 bacteria were eliminated after 2 days' relaying, and after three 

 days the reduction amounted to 99-6 per cent. 



Photographs of typical cultures obtained in these 

 experiments are reproduced in Plate I. 



At the same time a sample of mussels taken from the 



same place (the training wall) was laid down on the foreshore 



at Sunderland Point (see the chart). These mussels had not 



been examined before relaying, but they must have been 



as greatly polluted as those dealt with in the above 



experiment. After being relaid for two days they were sampled 



with the following results : — 



i ,r Ail (Plate 1, 7 red colonies, no colourless colonies. 

 1/OUtn J 90 



mussel " o q 



The reduction experienced was, therefore, similar to that 

 of the first experiment. 



Yet a further experiment was made with River Lune 

 mussels. Some of the fishermen at Glasson Dock wished me 

 to try relaying mussels at a point near to the railway station 

 there (see the chart). The place did not seem to me to be at 

 all suitable, but it was tried. A sample of mussels taken 

 from the same source, the Training Wall, was laid down. 



