OXYGEN CONSUMPTION IN THE PRESENCE OF CYANIDE. 407 



with thiosulphate. No loss of iodine was found, and indeed, 

 this possible source of error in the Winkler method w r ould seem 

 to have been greatly overrated (cf. Hale and Melia, '13). 



EXPERIMENTS ON PENNARIA. 



Pennaria tiarella, a common colonial hydroid of the Atlantic 

 coast, was selected as a representative of this group of coelenter- 

 ates. Large quantities of freshly collected material were avail- 

 able. Clean branches, free from visible plant growth, were cut 

 off, Caprella and other small animals which commonly live on 

 such colonies carefully removed, and the branches were then 

 placed in wide-mouthed bottles, and treated as described above. 

 The animals were always used within a few hours after they were 

 collected. 



TABLE I. 



ACTION OF POTASSIUM CYANIDE ON THE OXYGEN CONSUMPTION OF 



Pennaria tiarella. 



Oxygen Consumed, Cubic Centimeters per Hour. 



Six different lots of Pennaria were tested in this manner, as to 

 their normal rate of oxygen consumption and the rate in i/ioooo 

 and 1/25000 mol. potassium cyanide. The results are given 

 in Table I. In all cases, the rate of oxygen consumption is 

 reduced in the presence of cyanide. Unfortunately in the case 

 of this animal it could not be determined whether the effect was 

 reversible, since Pennaria deteriorates rapidly in the laboratory; 

 within twenty-four hours, the majority of the hydranths have 

 either fallen off or have lost their normal appearance. 



Since Pennaria exhibits very few movements, it is not possible 



