American Fislteries Society. 197' 



are slightly wanner than the surrounding water. This may he 

 inferred from the fact of oxidation in living animals, and direct 

 observations have corroborated it. In the thin gill filaments the 

 blood must cool to substantially the temperature of the water. 

 But after leaving them, oxidation occasions a slight warming. 

 In this warmer blood gas is less soluble and some of the air must 

 come out of solution as free bubbles. This process is continuous, 

 and finally enough air accumulates to plug the circulation. 



Bv subdividing the flow into very many fine streams the 

 Woods Hole water could be deprived immediately of its excess 

 of air and fishes Avould live in it without unusual symptoms. A 

 simple apparatus, a dishpan with the bottom punched full of 

 small holes and raised several feet above the tank it supplied to 

 give the streams a fall, served this purpose. It is to be remarked 

 that such an apparatus aerates water if it is lacking in dissolved 

 air and deaerates it if it has an excess. The process tends toward 

 a certain constant, which is the maximum amount of air the 

 water will hold at the temperature and pressure existing. 



The eggs and fry of the codfish were not affected by this 

 water w^liich was fatal to adult cod or adults of any species. This 

 is a rather remarkable and interesting fact. It is true that while 

 the eggs are in this water during almost the whole period of in • 

 cubation— some two weeks— the fry are in it only a few hours or 

 at most a few days. They are planted very soon after hatching, 

 yet they often remain in the water for a period which would be 

 fatal to adults, without appearing to be injured. The explana- 

 tion is to be looked for in their very different organization from 

 that of the adult. A newly hatched fry is far from being a full 

 fledged fish in other respects than size, and we can hardly sup- 

 pose it to maintain a temperature appreciably above that of the 

 surrounding water. This would remove the chief cause which 

 tends to release the gas once dissolved within the blood. 



The general features of this mortality present three salient 

 particulars. First, its severity. In the degree of supersaturation 

 existing at Woods Hole it was absolutely fatal. There was no 

 resisting the fatal outcome, no treatment or remedy while fishes 

 were within the affected water could be of any avail. With even 

 the hardiest and least susceptil)le species— the mummichog— it 

 was merely a question of time. Secondly, the simplicity of tho 



