Absolute rates of diffusion for carbon monoxide 

 across the walls of the pneumatophore from inside to out- 

 side are listed in table 3. In determining total surface area 

 the floats were treated as regular prolate spheroids. Dimen- 

 sional measurements are subject to the errors listed above, 

 but have comparatively less significance here. The total 

 volume of carbon monoxide dissolved in the syringe water 

 was corrected by means of blanks run on fresh seawater. 



It can be seen that rates of loss of CO across the 

 float walls are roughly equal to the rate of CO production 

 determined above. This further suggests that the float in 

 Experiment 6 (tables 1 and 3) was at best producing gas 

 only at a maintenance level. 



It is of interest to consider the nature of the diffu- 

 sion barrier presented by the delicate -appearing pneumato- 

 phore walls. The pneumatophore of the pelagic siphonophore, 

 Physalia, has been shown to possess a double layer of 

 chitin. 15 The pneumatophore of N. bijuga also has a double 

 wall with intervening septa and gastrovascular fluids. 



TABLE 3. DIFFUSION OF CARBON MONOXIDE 

 ACROSS PNEUMATOPHORE WALLS.* 



Experiment 



Surface Area 



Total 



Length of 



Absolute 



Krogh 



Remarks 



Number** 



of Float 



Dissolved CO 



Run 



Diffusion 



Diffusion 







(mm 2 ) 



in Syringe 

 (mm 3 ) 



(hr min) 



Rate 



(mmVmmVhr) 



Constant 

 (Start/End) 





6 



4.79 



0.23 



3:52 



0.012 « 0.01 



0.027 

 0.013 



CO 



produced 



7 



11.66 



29 



3:40 



0.007 = 0.01 



0.013 

 0.019 



No CO 



9 



1342 



1.43 



11 30 



0.009 = 0.01 







10 



10 14 



0.91 



11,30 



0.008 = 0.01 







*A11 at 7 0°C 

 **Experiment numbers coincide with those of table 1. 

 + Values for dissolved CO were corrected for reagent blanks 



23 



