150 Proceedings of Royal Society of Edinburgh. [sess. 
Experiment VI — 2000 cc. of the water from the bottle were 
partly oxygenated and returned to the bottle under nitrogen at 10-50 
and three fish introduced. One died during the night, one about 
11.30 on the next day, and the last fish, which seemed quite well, 
was taken out at 12.30. 
Oxygen in ccs. per litre — 
At 4 p.m. on first day =4 cc. 
At 10.30 a.m. „ second day =1 cc. 
Conclusions . , 
These experiments along with those of Hoppe-Seyler and Duncan 
seem to show that a fall in the amount of dissolved oxygen in 
water to below one-third of the normal amount, 2 ccm. per litre, is 
prejudicial and generally fatal to young salmonoids. 
When the surface of the deoxygenated water is exposed to an 
atmosphere containing oxygen as in Experiment IV., the fish 
frequently seem able to live by constantly coming to the thin 
layer of more oxygenated water at the surface. Some individuals, 
e.g., the largest fish in Experiment III., are able to sustain life 
for very prolonged periods in water containing only minimal traces 
of dissolved oxygen. Such fish are seen to lie very quietly at 
the bottom of the bottle. 
(. Issued separately May 2 , 1902 .) 
