GAS DISEASE IN FISHES. 369 
EFFECT OF SUPERSATURATED WATER UPON EGGS AND FRY. 
At Woods Hole sea water which was soon fatal to adults or fishes 
approaching maturity did notaffecteggsandfry. Eggs of the cod were 
incubated for some two weeks in such water and the fry remained in it 
until planted—not more than a few days at most, it is true, but a longer 
period than would suffice to kill adults—yet neither were injured or 
showed'any gas symptoms. It is probable, however, that very young 
fry are not necessarily immune under all conditions of supersaturation. 
Bubbles of gas have been noticed in the sacs of shad fry at fish cultu- 
ral stations. Mr. J. N. Wisner (1900) reports such a case at Havre 
de Grace, Md., and the circumstances point to a leaky suction pipe, 
but nothing is known of the degree of supersaturation, if any existed. 
Theoretically it seems difficult to avoid the conclusion that oxidation 
must be attended by an elevation of temperature even in so minute a 
creature as a newly-hatched cod fry; but this elevation must be infini- 
tesimal, for the consumption of energy necessary to maintain a tem- 
perature appreciably above the surrounding water is not supposable 
in the eggs or fry. As such an elevation of the blood temperature is 
the chief cause of gas precipitation in adults, its absence in the fry 
may be taken as strongly tending to explain their immunity. On the 
other hand, a sufficiently high degree of excess may be able to cause 
a separation of gas suchas above noted among shad fry, either by direct 
osmosis or via the circulation. 
METHODS OF PREVENTING THE GAS DISEASE. 
The proper aeration of water, by artificial means if not already 
accomplished by nature, has from the beginning been recognized and 
insisted upon by fish culturists as of fundamental importance. By 
aeration was meant the process of putting the water thoroughly in 
contact with the atmosphere, so that the dissolved air would be increased 
were there any initial lack. In a proper fish-cultural sense, aeration 
more strictly meant oxygenation, for it was the oxygen alone, the 
prime necessity of fishes, which was apt to be lacking. No cases, per- 
haps, are known in which natural waters have less than their proper 
or normal amount of nitrogen. But of course the aeration process 
adds both the atmospheric gases should the water be lacking in both. 
The readily observed distress and suffocation of fishes by the exhaus- 
tion of the dissolved oxygen in unrenewed water, the efficacy of even 
the simplest means of aeration in restoring the life-supporting quality 
to the water, as well as the generally understood necessity of oxygen 
to all animals, resulted naturally in an appreciation of the value and 
necessity of aeration. There were no observed facts from which one 
would infer the opposite condition in water, an excess of one or more of 
the air gases, nor were theoretical considerations likely to lead readily 
to its conjecture. It is improbable that any symptoms or mortality 
F. C. 1904—24 
