384 



2. TREATMENT FOR KEEPING FISHES ALIVE- 



Treatment A 



The water in this case was boiled in an apparatus (Fig. i) which 

 continuously boils and cools it, being run through at the rate of 500 

 cc. per minute. This removed all of the readily precipitable iron and 

 the excess of magnesium and calcium, thus reducing the total solids 

 to about what one commonly finds in the average stream; but the 

 water so treated still differed from stream w^ater in that the salts pres- 

 ent were nearly all carbonates, instead of a mixture of carbonates, 

 chlorides, and sulphates, and decidedly alkaline. The water was 

 aerated after boiling. The mortality became markedly less among 

 fishes when they were first brought in. but on the whole it was not less 

 than in water which received Treatment B. 



Treatment B 



In this treatment the water was aerated in an aerating device, so 

 as to give air saturation. This removed nearly all the free carbon 

 dioxide and rendered the water alkaline. In this the fishes lived fairly 

 well but became very sluggish, so that they were not suitable for be- 

 havior experiments. 



Treatment C 



Thinking that the above sluggishness might be due to the absence 

 of sulphates and the presence of carbonates only, a small quantity of 

 sulphuric acid was added to the water. This rendered it acid by dis- 

 placing some of the carbonic acid in the carbonates with the sulphate 

 radical. This treatment proved beneficial, but the requisite manipu- 

 lation was cumbersome. 



Treatment D 



For this treatment aerated water and direct tap water were run, 

 half and half, into the aquaria. This rendered the fishes active and 

 suitable for behavior experiments and the difficulties of manipulation 

 were reduced. Later a less complete aeration in the aerating device 

 shown in figure i was found to give equivalent results, and fishes 

 lived unusually well for months without attention. In this the water 

 was treated by running down twelve feet of incline at a rate of about 

 two liters per minute. It then usually contained sufficient oxygen to 

 support fishes and from 1-3 cc. of free CO2 per liter, and had lost 

 much of its iron and a little of its excess magnesium and calcium. 



