RHYTHMIC PULSATION 



347 



TABLE 11 



duration (a) of pulsation and (b) of irritability to mechanical 

 stimulation, in the several salt mixtures studied, are given in 

 table 11. By way of comparison, data taken from Bethe's 

 account of the effects of sea water constituents upon pulsation 

 in medusae (Bethe, '08) are given in the last column of table 12. 

 The cloacal ends of holothurians are in some ways a better 

 indicator for use in studies of this nature than are medusae, 

 since the former pulsate continuously and not, as the jelly fishes 

 do, in more or less interrupted groups of movements. 



TABLE 12 



Summarizing Ihc residtf^ of lesls with salt mixtures. For details, sec text 



NaCl 



NaCl + CaCl-, 



NaCl + KCl 



NaCl + KCl + CaCIa 



NaCl + MgCla 



NaCl + KCl + CaClo + MgCls 



van't Hoff solution 



"7" made alkaline 



9 Sea water. 



95 



47 



150* 



1 



1200± 



:10 days) 



In column 'R' are given the corresponding data for the pulsation of the medusa 

 Rhizostoma (Bethe, '08, p. 573). 

 * This solution contained CaCOs. 



A notable peculiarity of the pulsation curves of pieces immersed 

 in NaCl solution (compare previous section, and figure 30) is 

 the irregularity of the pulsation rate. During the early history 

 of pieces in NaCl, the pulsation rate was also very low. By 

 reference to figure 31 it will be seen that, in the experiments 



