250 MORRIS M. WELLS 



a O.OIN solution of this salt, and the graphs show this negative- 

 ness to be rather definite. The fishes turned back from the 

 CaCl2 end at a point which the conductivity measurements 

 showed to be about 0.0065N. Some of the apparently normal 

 fishes, however, gave positive reactions to O.OIN CaCl2 and in 

 working out this point over 150 experiments were performed. 

 A very interesting relation between starvation and the reaction 

 of fishes to CaCl2, and probably some other salts, was found to 

 exist. The experiments showing this relation will be discussed 

 on a subsequent page under the heading, ''Physiological states 

 and the reactions of fishes" (p. 260). 



e. Magnesium chloride. Normal fishes reacted negatively to a 

 O.OIN concentration of this salt, but as with calcium, there was 

 a number of instances where the reaction seemed to be reversed. 

 Normal fishes were also negative to a 0.02N concentration, which 

 however did not prevent a few of the fishes from showing a posi- 

 tive reaction, as they had done with the O.OIN solution. 



2. Reaction to the nitrates 



The nitrate experiments, with tke exception of part of those 

 with calcium, were performed at Illinois. The experiments with 

 the nitrate of calcium were performed largely at Chicago, enough 

 being repeated at Illinois to correlate the reaction in the two 

 waters. 



a. Ammonium nitrate. Practically all the fishes used were 

 negative to this nitrate, which is very stimulating to them, in 

 tap water, as will be shown in the resistance experiments. They 

 did not, however, avoid the salt end with as much precision as is 

 displayed in the case of a number of the other salts, and in one 

 experiment, a 25-gram crappie, although giving a fairly strong 

 negative graph, still was overcome by the salt, lost control of 

 its movements, and 'scooted' about the tank, finally leaping over 

 the edge onto the water table. Sixteen experiments were per- 

 formed; of thvise fourteen show decidedly negative reactions, 

 while two, one with a 3-gram blue-gill and one with a 6-inch 

 bull-head, show positive reactions. These two fishes were not 



