152 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



tanks, has many features to recommend it for practical use. Steam, instead of electric 

 pumps, would also have this especial advantage, that the power would be under the 

 immediate control of the aquarium management, and not liable to possibly fatal inter- 

 ruptions through failure of connections, especially at night — an accident which we 

 barely escaped several times. 



The fresh-water system, it will be remembered, was constructed for a continuous 

 inflow of lake water, which ran away again after passing through the tanks. By this 

 system an enormous quantity of water was required, amounting in our aquarium, during 

 the warmest weather, to no less than 40,000 gallons an hour. Even at this rate it took 

 nearly three hours to renew the water in the tanks, and a much greater supply would 

 have saved us some heavy losses consequent upon trouble with a protozoan parasite 

 presently to be described. In a permanent aquarium the cost of so large a quantity 

 of water and the expense of filtration would be an important item in the maintenance. 



By this method, also, everything depends upon the continuous integrity of the 

 filter. We found the lake water to be heavily infected all the seasons through with 

 the germs of fungous fish-disease. These fungous spores were largely removed by 

 our alum filter, even when worked at two or three times its normal capacity; but, on 

 the other hand, even a few hours disability of the filter not only resulted in an offensive 

 clouding of the water, but was invariably followed by an outbreak of fungous disease 

 all along the line of our tanks. It has consequently seemed to me possible that a 

 closed circulation like that ou the salt-water side might have given us a more perfect 

 command of the aquarium and its contents, and possibly at even less expense than was 

 involved in the system we used. If it had proven possible, under our conditions, to 

 establish water plants generally in our tanks, this would, of course, have assisted in 

 aeration, and a much smaller flow of water would have sufficed. It would have been 

 necessary, however, even with "balanced" aquaria, to keep up a considerable move- 

 ment of water through tanks carrying as heavy loads as ours, especially at night, 

 when oxygen comes off slowly or scarcely at all from water plants, and fishes are 

 consequently more liable to death from suffocation. For the Salmonidce, especially in 

 summer, a rapid and abundant flow is necessary; and for fish affected with the trout 

 parasite, presently to be described, the water should run through the tanks in torrents 

 day and night. 



The gredt success of the aquarium season was the transportation and main- 

 tenance of our excellent collection of marine animals in their normal state of health 

 and comfort. Ocean forms were never before carried alive over distances approaching 

 those from Chicago to Florida and the Pacific coast, and, although many specimens 

 fell by the way, the ratio of the lost to those delivered in good condition rapidly 

 diminished with the experience of the car captains and their crews. The most 

 successful trip of the summer, in fact, was that made by Gapt. Lamson with a small 

 load from Puget Sound. 



The original supply of sea water was gradually increased by additional amounts 

 brought in by the cars as they came with their loads, and by pouring into the filter 

 from time to time a few hundred gallons of a simple solution of Turk's Island salt. 

 The fixed density maintained was 24° by scale. * 



' The total amount of .salt water received from the sea was approximately 50,000 gallons. To 

 tliis 8,820 gallons of salt solution were added from May :> to Scptemher 21, the largest, amount at any 

 one time being 1,080 gallons. Five hundred gallons of fresh water were used from October 1 to 9 to 

 make good losses by evaporation and to maintain the proper density. 



