204 Thirty-Second Annual Meeting 



the fins. According to the species of fish in which it occurs it 

 appears in various ways. To test this, a week or two ago I ar- 

 ranged an aquarium here in the hatchery, according to the plan 

 advised by Mr. Marsh, allowing the water to pass through his 

 deaeration apparatus before passing into the aquarium, and put 

 in a considerable number of fish. In other aquaria I put control 

 fish to notice the difference. I found that the external bubbles 

 which Mr. Marsh describes and the bubbles of gas in the blood 

 vessels, do not appear in the fish which are in the water subject- 

 ed to this deaeration process, but I do find the "popeye" occur- 

 ring. There is a fish in No. 1 aquarium over there now in which 

 the bubbles of gas are forming behind the eye in just the way 

 they do in the other aquaria, so that it seems to me we are deal- 

 ing with two sorts of gas disease here, and we ought to distin- 

 guish between the two. 



Mr. jSTevin : Did you ever see air buljbles on the rainbow 

 trout and see them floating on their backs ? 



]\Ir. Marsh : No. At the time I was at Erwin there were no 

 fry with sacs, and whether such fry had these gas bubbles or not 

 I don't know. 



Mr. Lydell : I would like to ask Mr. Marsh if it is possible to 

 take an air pump and pump too much air into water for fish ? 



Mr. Marsh : I think that is purely a question of how deep 

 the water is. In an ordinary can I do not think you could get 

 sufficient excess to harm the fish at all ; but if you had a can 

 eighteen feet deep or perhaps not quite so deep, and pumped a 

 continuous stream of air to the bottom, I believe it would kill all 

 the fish in the can after a while ; the pressure of this high column 

 of water drives the air into the water in excess. The water in the 

 ordinary fish can seldom lias an excess. I think there is a depth 

 of only two or three feet and that would make an additional pres- 

 sure of only a pound and a half about. 



Mr. Titcomb : I can give a little experience about this super- 

 abundance of air in aquaria in connection with the ordinary ones 

 used in drug store windows. I know of two instances where a 

 beautiful lot of trout on exhibition in an aquarium about six feet 

 long by about two or three feet wide in a drug store window, were 

 all killed. The first lot of trout suddenly Jumped out onto the 

 floor as if at a signal. The aquarium was restocked and covered. 



