350 W. J. CROZIER 



efficient in NaCl + KCl + CaCls than in the same + MgCl.. 

 The depressant action of salts which diminish the active number 

 of Ca ions has frequently been assumed to be due to their effect 

 on the Ca- concentration, but the results of Salant and Hecht 

 ('15) indicate that this conclusion is not well founded. Experi- 

 ments of the following type showed that these well known rela- 

 tions obtained also with the cloaca of Stichopus: 



Experiment 1^5.2. June 29. Five preparations from Stichopus moe- 

 hii were allowed to begin pulsating in sea water. They were then trans- 

 ferred to a 0.1 per cent solution of oxalic acid in sea water. Pulsations 

 of the sphincter ceased in 3 minutes, though the cloaca and body wall 

 contracted rhythmically for about 4 minutes longer. The sphincter 

 remained open; it contracted once in response to each light touch, for 

 5 minutes more. 



Experiment 75.2. July 20. Three cloacal preparations immersed 

 in a solution of the following proportional composition: 100 cc. sea 

 water + 3 cc. y^ tartaric acid. Pulsation lasted 15 to 20 minutes. 

 Ceased with the cloaca and sphincter in the open phase. 



Experiment 74-2. July 20. Five cloacal preparations immersed in 

 a solution of the following composition: 100 cc. sea water-|- 5 cc. m. 5/8 

 sodium citrate. Pulsations continued for a little over two hours, ceas- 

 ing in the open phase. The movements, while they lasted, were of 

 almost abnormal amplitude and vigor. Cessation found the sphincter 

 in the open phase. "^^ 



Experiment 74--1- August 3. Three cloacal preparations immersed 

 in a solution of the composition 100 cc. sea water -|- 2 cc. m 5/8 CaCL. 

 Pulsations continued for about 5 hours, at the end of which time the 

 sphincters were all tightly closed, though they responded to a touch 

 by opening and closing once. 



Further increase in the amount of CaCb in sea water stopped pulsa- 

 tion (with the characteristic calciimi tetanus) in a shorter time. 



The efficiency of salt mixtures in preserving pulsation was 

 notably improved by making them alkaline, especially with 

 NH4OH. NH4CI was found to be very toxic, but solutions of 

 the composition: 100 cc. sea water + 2 cc.^ NH4 OH preserved 

 pulsation for about 20 hours, when the volume of solution 

 for each piece was 500 cc. NaOH or KOH substituted for the 



'^ In this solution the tube feet moved incessantly, in sharji contrast to their 

 usual quiescent condition in sea water. 



