SEA-FISHERIES LABORATORY. 135 



tanks at the rate of about 1 litre per five minutes. Samples of 

 the mussels were taken after treatment of this kind for one, 

 two, and four days. 

 First Sampling. After 1 day. 



l/50th mussel contained intestinal bacteria. 



55 55 " 55 55 



55 55 -L 55 55 



Mean per mussel = 16-6. 



Second Sampling. After 2 days. 



l/50th mussel contained 4 intestinal bacteria. 



Mean per mussel =116. 



Third Sampling. After 4 days. 



l/50th mussel contained 6 intestinal bacteria. 



55 55 * 55 55 



55 55 " ,, ,, 



Mean per mussel =116. 



Colourless colonies appeared in the plates made from the 

 crude mussels, but none was seen in the plates made from the 

 treated mussels. 



The sewage bacteria present were therefore reduced by 

 98-5 per cent. 



This experiment was not repeated. The same results had 

 been obtained, as on a former occasion, by Mr. Scott, and 

 little more information was to be attained by laboratory 

 trials. It might have been possible to reduce still further, 

 the time necessary for sufficient cleansing, and it might also 

 be desirable to observe what degree of cleansing takes place 

 when mussels are allowed to remain in various volumes of 

 standing sea-water, and for variable periods. But on 

 considering the difficulties which are likely to be encountered 

 in applying the principles of these methods on a large scale, 



