RHYTHMIC PULSATION 



345 



TABLE 9 



Effects of single salt.< 



Averages from five series of tests. The figures in parenthesis opposite NH4CI 

 and KCl mean that, while the sphincter of cloacal pieces immersed in these solu- 

 tions did not pulsate, the body part did so, irregularly, for the number of min- 

 utes noted. 



TABLE 10 



Summarizing the results of tests made upon five isolated cloacal ends of Stichopus 



moebii with each of the salts indicated 



Time — Minutes. 



For the chlorides of the alkali metals and radical (table 10), 

 the order 



Na > Li > NH4 > K 



was obtained with reference to their ability to preserve pulsa- 

 tion and irritability. The significance of this series, in terms 

 of the aggregation state of protoplasmic materials, has been 

 treated in a comprehensive manner by Hober ('14, pp. 471 et 

 seq.). A beautiful demonstration of the action of the cations 

 of neutral salts in this series has recently been given by Spaeth 

 ('13) for the chromatophores of Fundulus. In solutions of NaCl 

 and LiCl the pieces came to rest with the anal sphincter in an 

 expanded condition but with the radiating cloacal muscles con- 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 20, NO. 3 



