260 



W. C. ALLEE 



TABLE 1 



A comparison of chemical analyses of Chicago and University of Illinois tap water. 

 Analyses of solids in parts per million and gases in cubic centimeter per liter 



V. OF I. tap' 



Potassium, K 



Sodium, Na 



Ammonium, NH4 



Magnesium, Mg 



Calcium, Ca 



Iron, Fe 



Aluminum, Al 



Silica, Si 



Nitrate, NO3 



Chlorine, CI 



Lead, Pb , 



Sulphuric acid, SO3 



Oxygen, O 



Free carbon dioxide 



Half bound carbon dioxide. 



2.6 

 29.0 



2.3 

 34.9 

 70.1 



1.0 



1.3 

 18.9 



0.7 



3.5 



0.00 



2.3 



0.12< 

 18.0 

 101.12 



1 Shelford and AUee '13, table 4, p. 217. 



2 Bartow '06, p. 34. 



3 Bartow. 



^ After allowing air to bubble through the water, the dissolved oxygen was 

 raised to air saturation (5.5 to 7 cc. per liter). The free carbon dioxide was 

 removed and the half bound carbon dioxide was reduced to 88.58 cc. per liter. 



71 per cent of 150 trials, and seven days later, 87 per cent of 

 150 trials were positive. There was little mortality — practically 

 none after those injured in shipping had died. This indicates 

 that the change in the chemical content of the water either did 

 not affect the rheotactic response or that the isopods quickly 

 became acclimated. 



The animals under experimentation were placed in glass dishes 

 which held about 1.5 liters of water. These were placed in run- 

 ning tap water to insure more even temperature. The stock 

 was kept in a glass-sided room and all tests were performed in 

 a part of this room curtained to exclude direct light. The 

 majority of the tests were made from 8 to 12 a.m. Records were 

 taken of the daily reactions of twenty individuals covering a 

 period of from three to seventy-five days. This period did not 

 include the breeding season. 



