RESPIRATION OF DYTISCUS MARGINALIS L. 347 



this Apo2> APN2 must have the value of 421 mm. Hg, Actually 

 this value is only 130.8 mm. Hg. This proves that oxygen will 

 diffuse in quicker than N2 diffuses out, even when we do not take 

 into consideration the higher value of CO2 in the bubble. 



/3. In this way it has been proved that oxygen really diffuses 

 faster into the bubble than nitrogen diffuses out. Tt seems even 

 possible that this inflow of oxygen may compensate to a certain 

 extent for the decrease in volume of the bubble. 



Another question, however, arises: Will this inflow of oxygen 

 enable the animal to stay under water? In other words: Will 

 the inflow of oxygen compensate the consumption of oxygen of 

 the animal and have in that way a vital biological importance? 

 In that case the only reason for the animal to move upwards 

 would be the lack of nitrogen, though this seems to be a paradox. 

 This question has been denied by Ege, and I completely agree 

 with him, though I believe that it can be demonstrated in a much 

 more simple way. 



According to Ege's figures, one Dytiscus consumes in one 



minute 8 mm.^ of oxygen. The quantity which diffuses in can 



T S Ai} 

 be calculated by means of Bohr's formula: M = — — '- — -. 



y60 



Taking p = 136 mm., and s = 10 mm. 2 (as Ege did), 



0.029 X 10 X 136 ^ 52 ^^3 



760 



of oxygen diffusing in. The discrepancy between these two 



figures is evident. 



7. In this way we see that the term 'biological importance' 

 which Ege introduced is ambiguous and should be avoided. As 

 far as the oxygen economy is concerned, the oxygen diffusion has 

 no 'biological importance'; that it plays a role in preventing the 

 volume of the bubble from decreasing too quickly has been shown 

 in the given calculations. 



5. The possibility which occurred to me in the beginning that 

 by the inflow of oxygen the volume of the bubble might increase 

 so that the animal would be obliged to move upwards simply to 

 get rid of its superfluous air — in that way the frequent escaping 



