SEA-FISHERIES LABORATORY. 139 



bulkheads were placed at each end so that the further entrance 



of water could be prevented after the tank had been filled. 



The tank could be moored at any place selected. A sample 



of mussels from Aberdovey Channel, near the Pier, was taken 



and placed in the tank, and the latter was then moored above 



Trevri Point. (See Mr. Durlacher's Chart in the Report for 



1913 for these localities.) After being relaid for three tides the 



mussels were sampled. The shellfish lived well in the tank, 



and had attached themselves to each other and to the wooden 



sides. 



First sampling. The original, un-relaid mussels. 



., .„.,. (Plate 1, 13 red colonies, no colourless colonies. 

 l/50tn I 9 ik -i 



mussel I " «' J? " { 



Mean number of sewage bacteria per mussel = 735. 

 Second sampling. Relaid for three tides. 

 , IK _ , (Plate 1, 13 red colonies, no colourless colonies. 



VoOth 2 10 



mussel o io 



V 55 °5 10 55 55 55 



Mean number of sewage bacteria per mussel = 600. 

 The experiment was repeated later in the year. A sample 

 of mussels was dredged from near Penhelyg Point, and was 

 relaid in the tank, the latter being moored on the beach near 

 the life-boat house at Aberdovey (see Mr. Durlacher's chart). 

 At both this place and the one in the other Aberdovey experi- 

 ment, water circulated through the tank for about four to six 

 hours during each tide. The tank came adry during ebb-tide, 

 and it was expected that before the time when the number 

 of sewage bacteria had increased notably in the water of the 

 channel, the tank would be out of the water. 

 First sampling. The original, un-relaid mussels. 



(Plate 1, 13 red colonies, no colourless colonies. 



mussel o' o n 



I, 55 O, O ,, U ,, ,, 



Mean number of sewage bacteria per mussel = 485. 



