140 



PHYSIOLOGICAL KEGULATIONS 



Evidence of various sorts indicates that dissolved constituents 

 (ions) of body fluids and of sea water are in these tests not exchang- 

 ing between body and environment. Hence desiccation in concen- 

 trated sea water is equivalent to desiccation by evaporation; the 

 recovery in sea water following actual evaporation was tested and 

 occurred at the same rates as above. Excesses that were obtained 

 by previously injecting distilled water also showed the same re- 

 covery rates as those obtained by previous swelling in diluted sea 

 water. 



Gephyrean Worm 

 Phascolosoma 



2 3 



Hours 



Fig. 86. Rate of net water exchange (% of Bo/hour) in relation to time after 

 return of worms to normal sea water. Phascolosoma at 23° C. Same data as in figure 

 85. 



While recovery by intake is faster than recovery by output, yet 

 it is commonly believed that the same forces of water transfer 

 through the same integument are concerned. Actually the kinetics 

 of the two exchanges also differ, as well as the values of h in the 

 above equation ; for during water gain h is constant, during loss Ji 

 is not constant. 



Since I am describing the rates of water exchange, I preserve 

 ± AW as abscissae (fig. 87). For other purposes, in view of the 

 supposed relationship of BW/At to osmotic pressure in Phascolo- 

 soma, l/(Pi -Pe) might be used as abscissae of figure 108 instead 

 of ± AW; the internal osmotic pressure (P.), being in turn, com- 

 puted from l/CB-b) in which B is the body volume and b an 



