RHEOTAXIS, RESISTANCE TO POTASSIUM CYANIDE 



401 



time) for a week before killing them in cyanide at the same tem- 

 perature. Under these conditions there was a shortened sur- 

 vival-time but the variations in temperature were too great for 

 the results to be anything but indicative. 



In the work with lowered temperature the isopods had been in 

 a temperature of 17 to 19° and were placed in an ice-chest with the 

 temperature at 8 to 14°. After a week under these conditions they 

 were killed in potassium cyanide, 0.0002 molecular solution, at the 

 same low temperature. The isopods at the usual temperature 

 (table 1) showed a higher rate of positive rheotaxis and of efficiency 

 in the current than did those from the lower temperatures and 

 hence would be expected to give a shorter survival-time regardless 

 of the temperature change, but the difference is entirely too great 

 to be altogether accounted for in this way. 



It is to be expected that the chemical activity of the cyanide at 

 low temperature would be less than at a higher temperature, 

 but it is highly improbable that the great differences in survival- 

 time at the different temperatures could be due to this cause 



TABLE 1 



Showing the effect of different factors upon the survival in potassiutn cyanide ivith a 

 view to testing whether the resistance to cyanide bears any relation to the metabolic 

 condition of isopods 



