RHEOTAXIS OF ISOPODS 205 



tarily on filter paper and placed on a cover glass with no water 

 added except that which clung to the animal. An amber ring 

 about three millimeters high was placed around the isopod and 

 this was covered with wire gauze to prevent extended movement 

 of the animal while in the respiration chamber.* This precau- 

 tion was the more effective since isopods are strongly positively 

 thigmotactic and will rest quietly for extended periods when 

 they are able to place their bodies in an angle of their container. 

 When comparisons were made in the Biometer, isopods of 

 approximately the same size were selected in order to guard 

 against a greater production of carbon dioxide due to greater 

 mass. The isopods were left in the respiration chambers for 

 only ten minutes during the quantitative work but in the quali- 

 tative results, tested in the Biometer, the isopods were left as 

 long as thirty minutes. The fact that isopods survived nine 

 daily tests and showed no ill effects of the handling demonstrates 

 there is little danger to the animal in such treatment. 



THE RELATION BETWEEN CARBON DIOXIDE PRODUCTION 

 AND RESISTANCE TO POTASSIUM CYANIDE 



The work upon the relation between carbon dioxide output 

 and the resistance of isopods to potassium cyanide was quali- 

 tative only and was carried on to ascertain whether or not the 

 resistance of isopods to the cyanide is a safe index of their met- 

 abolic activity. Child ('13, '13a) found that in Planaria the 

 susceptibility of animals or pieces of animal to 0.001 mol. solu- 

 tion of potassium cyanide varied in general with the rate of 

 metabolism. Estimation of carbon dioxide production on in- 

 dividuals and pieces (of the same species) made at Dr. Child's 

 request by Tashiro with the aid of his Biometer showed that 

 carbon dioxide production ran parallel with susceptibility to 

 potassium cyanide, and so afforded a confirmation of Child's 

 conclusion concerning the relation between susceptibility and 

 the rate of metabolism. 



2 We appreciate the roughness of this method for checking spontaneous muscular 

 movement, but it was out of consideration for us to devise an automatic recorder 

 for bodily activity such as is necessary in order to make accurate metabolism 

 experiments with mammals. The principal source of error in determining the 

 amount of carbon dioxide given off by isopods lies in the fact the spontaneous 

 muscular movements were not under complete control. With the device described 

 above and by constant, careful observation with a hand lens of the animal during 

 the experiment, we convinced ourselves that we had sufficient control of the move- 

 ments of the animals to answer the needs of our experiments. 



