which time they grew from about seven eighths 

 of an inch to perhaps an inch and three eighths 

 in length, and became very plump, vigorous and 

 much more active and able-bodied than at first. 

 During the month of June the weather became 

 gradually very hot; and as my tanks were so 

 situated that I was unable to give them the ad- 

 vantage of the cooling night air, the temperature 

 of the water rose day by day until it reached 

 80 degrees. Up to that temperature, much to 

 my surprise, the trout had remained perfectly 

 strong and vigorous. Finally however, when the 

 temperature of the water had passed 81 and was 

 approaching 82 degrees, I found one of the trout 

 dead and the other swimming in circles at the 

 surface. Had 1 been able to properly cool the 

 room at night I am satisfied that I might have 

 kept those trout in excellent condition through- 

 out the summer. I doubt whether this species 

 has ever before been maintained in health in 

 stagnant water for an entire week during which 

 the water temperature advanced from 70 to 80 

 degrees. And I am inclined to the belief that 

 with super-abundant oxygen from vigorous 

 growing plants, and a sut^lcient supply of their 

 natural food, our native brook trout, the most 

 sensitive to high temperature of all our fishes, 

 may be maintained indefinitely in stagnant water 

 up to 75 degrees. This suggests a matter which 

 1 have never seen referred to in any book or 

 article on aquaria, but which I have had con- 

 stantly in mind in my own experiments; that is, 

 the possible complete balance of the entire life 

 relations of a tank, inclusive of food supply. 



In the case I have described such a balance 

 existed. Owing to the large area of the tank, 

 dense cover aiforded by plants, and reduced 

 stocking of fish, the minute life was multiplying 

 faster than the two trout were able to capture 

 and consume it. In such a relation we have, not 

 merely the crude balance of animal life to the 

 aerating power of the plants, but a finer and 

 more beautiful balance between the fishes and 

 the food supply; a balance which is quite possi- 

 ble of maintainance during the summer season, 

 at least, when the minute forms of life multiply 



75 



