SEA-FISHERIES LABORATORY. 143 



and exhibiting motility, was added to each. The number 

 of bacteria in one of the flasks was estimated, it was about 

 3,000. Chlorine water was then added to each of the other 

 flasks in quantity enough to make solutions of 1, 3, 5, and 7 

 parts per million, and the flasks were allowed to stand at 

 ordinary laboratory temperature for 24 hours. One c.c. of 

 the culture was then taken from each and plated in neutral- 

 red, bile-salt, lactose agar. All the plates were sterile. 



One part per million of chlorine seems, therefore, to be 

 enough to secure the destruction of most of the ordinary 

 bacteria present in sea- water, though there is no object in 

 using so very dilute a solution. The next point was to 

 determine what concentration the mussels could stand without 

 injury. Some bleaching powder solution was first of all made, 

 and this was added to aquaria containing mussels, but these 

 rough trials were unsatisfactory. Finally chlorine water was 

 made from a mixture of potassium dichromate and hydro- 

 chloric acid, and after washing in tapwater, the gas was 

 absorbed in distilled water. A standard solution of thio- 

 sulphate (and one of pot. dichromate for standardisation of 

 the thiosulphate) were made, and the strength of the chlorine 

 water was estimated before each experiment. Several glass 

 aquaria were filled with sea-water — each of them held about 

 ten litres — and then dilute chlorine water was added so as 

 to produce solutions having, very approximately, the concentra- 

 tions of 4, 6, 8, and 10 per million. The chlorine solution 

 and the sea-water were mixed, and mussels were added, and 

 the behaviour of the shellfish noted from hour to hour. There 

 was some doubt as to whether those in the solution of 10 per 

 million opened their shells — I think they may have done so — 

 but all the others functioned normally, even spinning byssus 

 threads and attaching themselves to the glass of the aquaria. 

 Even in the 4 per million solution, the smell of chlorine could 

 be detected at the beginning of the experiment. Evidently, 



