254 MORRIS M. WELLS 



ments with 0.01 N Na2S04 in moderately acid water were run. 

 All of them show decidedly negative reactions. In a number 

 of experiments the attempt was made to drive the fishes into 

 the salt end, but with no success, except in one case, where a 

 20-gram crappie was driven into the salt end and remained there 

 for 5 minutes before swimming back into the tap water end. 

 The blue-gills could not be driven as they would dart back past 

 the driving rod in every case. If these fishes were dropped into 

 the salt end they showed much disturbance and very soon swam 

 into the tap water end. In one experiment 8 small blue-gills 

 (2-4 grams) were placed in the tank and readings of their posi- 

 tion taken every 30 seconds until 25 readings had been made. 

 The percentage of time spent in the thirds of the tank were, 

 salt third 13 per cent, middle third 36 per cent and tap water 

 third 51 per cent. Thus fishes are negative to O.OIN sodium 

 sulphate in moderately acid tap v/ater but are positive to this 

 concentration in strongly acid water. The explanation of this 

 latter reaction must lie in the antagonism between the salt and 

 the acid. 



d. Calcium sulphate. These experiments (11 in all) were per- 

 formed at the University of Illinois. The reaction in moderately 

 acid water was negative in all but two cases. In one of these a 

 fish which had at first selected the tap water end, was driven 

 into the salt end, where it remained for the remainder of the 

 experiment. An experiment in which 10 small blue-gills (2-4 

 grams) were placed in the tank and their positions read at 30- 

 second intervals, showed percentages as follows: Time spent 

 in salt third 25 per cent, in middle third 32 per cent and in the 

 tap water third 43 per cent. 



e. Magnesium sulphate. Ten experiments with this salt were 

 run at Chicago. All showed a negative reaction to the O.OIN 

 concentration and in most cases the reaction was very decided 

 (usually above 80 per cent in tap end). The experiments were 

 not repeated at Illinois. 



