1915] Edgar G. Miller, Jr. 199 



{U. S. Fisheries Biological Station, Woods Hole, Mass.) Apart 

 from the technical difficulties involved in the investigation of the 

 gaseous metabolism of aquatic animals, the inability to control their 

 behavior is the strengest drawback in such studies. It is a well 

 known fact that muscular exertion of any kind increases the gaseous 

 exchange very considerably ; and unless a uniform base line, un- 

 affected by bodily movements, can be established, the influenae of 

 different factors cannot be determined with any degree of accuracy. 



To overcome this latter difficulty I have chosen, for experiment, 

 the flounder, which normally does not move about but rests, some- 

 times for hours, in the same position. The flounder, and a few other 

 fish, have the habit of lying quietly on the bottom of the receptacle 

 without changing their positions and, if not disturbed, move neither 

 fins nor tail. These aquatic animals are therefore practically ideal 

 subjects for metabolism investigations. 



Owing to lack of special apparatus for determining the carbon- 

 dioxid Output and oxygen consumption, I was obliged to limit my 

 research to the oxygen alone. Determination of the carbon dioxid 

 in sea-water, by an easily available method, is still an unsolved 

 problem. Oxygen, on the contrary, can be measured very ac- 

 curately by means of the Winkler method. The latter is described 

 in detail in special manuals and need not be given here. It will 

 sufiice to say that it is an iodometric method and requires very little 

 time. As an illustration of the accuracy of the method I may 

 quote a few duplicate analyses of the oxygen content of sea-water 

 in the Laboratory of the Bureau of Fisheries at Woods Hole. On 

 different days the following results were obtained, expressed as 

 CG. of oxygen per Hter: 



ABC 



S.58 5-95 5-52 



5-54 5-95 5-55 



The method of studying the oxygen consumption by the 

 flounder was very simple. The fish, usually of small size, was put 

 in a vessel of known volume filled with sea-water, of which a sample 

 was analyzed for oxygen. The vessel was then tightly closed, the 

 time recorded, and temperature of the water noted. From the 

 percentage of oxygen the total quantity dissolved in the vessel 



