246 Papers from the Department of Marine Biology. 



oxygen was readmitted. In one experiment an umbrella was kept 7 

 hours at zero O2 concentration, then 3 hours with O2 and a trapped 

 wave, and 7 hours at zero O2 concentration, during which it gave out 

 no CO2 or other acid products affecting the pH perceptibly; 30 seconds 

 after it was taken out of the 02-free chamber a trapped wave was started 

 and this constantly increased in ampUtude for 10 minutes, at the end 

 of which time the amplitude was normal. 



Oxygen was removed from sea-water in various ways, with the air- 

 pump and agitation, by boiUng, and by allowing a cassiopea to remain 

 in it until the pulsations ceased, as seen through a peep-hole in such 

 a way that photosynthesis was practically avoided. In no case did 

 the analysis show less than about 0.05 c.c. per liter, but that amount 

 probably entered with the KI and MnCl2 solutions and around the 

 ground stopper of the analysis bottle. At any rate, we should con- 

 sider 0.05 c.c. to be within the limit of error of the method if no correc- 

 tion were made for O2 in the reagents. 



The variation in metabolism after removal of the manubrium and 

 initiation of a trapped wave is shown in table 21. The diameter of the 

 umbrella was 11.5 cm. at the beginning of the first experiment and at 

 the beginning of each experiment the pH was 8.2 and the O2 per liter 

 4.5 c.c. It is evident that the metabolic rate may vslyj rapidly for 3 

 hours after the manubrium is removed and the trapped wave is started ; 

 therefore, in the subsequent experiments the umbrella was not placed 

 in the respiration chamber until these 3 hours had passed. The same 

 umbrella used in the above experiments but 21 hours after the opera- 

 tion was used to determine the effect of reduced oxygen concentration. 

 The average O2 concentration during the experiment was 1.5 c.c. per 

 liter and the O2 used per hour 1.03 c.c, being a decline of 20 per cent 

 in rate of oxidation, mth a reduction of the oxygen-concentration to 

 about half its original value. This and some later experiments are 

 as shown in table 22. 



These determinations show that oxidation is reduced about 20 per 

 cent when the O2 concentration is reduced about 50 per cent; or the 

 oxidation increases about 25 per cent when the O2 concentration is 

 increased about 100 per cent. 



The above experiments show that the rate of oxidation varies with 

 the tension of oxygen in the sea-water constantly circulated against 

 the surface of the epithelium in which oxidation takes place. In the 

 total absence of oxygen no measurable quantity of CO2 or other acid 

 products are given out, and we may infer that the metabolism is sus- 

 pended. If oxygen is readmitted after a suspension of the metabolism 

 for 7 hours, the rate of metabolism rises apparently to the normal 

 within 10 minutes. No anaerobic processes were detected during 

 absence of oxygen for 7 hours, but in the absence of oxygen for 16 hours, 

 anaerobic or hydrolytic processes take place. No evidence was found 



