RHYTHMIC PULSATION 



339 



vidual cases is plotted in figure 28. The tests indicated that 

 above 50 per cent concentration, mixtures of sea water with 

 rain water tended to preserve about the normal pulsation-rate, 

 but that in these mixtures the duration of pulsation was less than 

 that of the control (100 per cent); below 50 per cent sea water 



Effects ofsei/era/ concc/y/rat/ons 

 o/ 

 'Seau/ater. 



/'95 



28 



zoo 300 400 



TTme of immer^/on —//?/>?. 



the pulsation-rate and duration fell off rapidly. Above 100 per 

 cent concentration the duration of pulsation was also curtailed. 

 The general nature of these effects did not differ whether (a) 

 the cloacal pieces were immersed in the solution immediately 

 after amputation, or (b) after pulsation in the amputated end 

 had been allowed to start in sea water; procedure 'a' was fol- 

 lowed in the cases recorded. ^^ In these experiments the pieces 



'^ With this method of immersion, the pieces were in the condition shown at 

 A in figure 12, and the solution therefore had free access to the interior parts of 

 the cloacal end. 



