86 M. E. COLLETT 



Acids of group 1 : 



Paramecium : Mg > Co > Mn > Cd = Ni = Zn 

 Euplotes: Mg > Mn > Co > Cd > Ni = Zn 



Acids of group 2: 



Paramecium: Mg > Mn > Co > Cd > Ni = Zn 

 Euplotes: Mg > Mn > Cd > Co > Ni = Zn 



6. Antagonistic power is somewhat limited by the toxicity of 

 the salts concerned. At a concentration of 0.01 M the toxicity 

 of the pure salts is : 



Paramecium : Ca < Sr < Mn < Ba < Mg < Co < Cd < Ni = Zn 

 Euplotes: Ca < Sr < Mn < Mg < Ba < Co < Cd < Ni < Zn 



When combined with NaCl, toxicity is reduced for all except Sr, 

 Cd and Co (Euplotes). 



VISIBLE CHANGES IN THE PROTOPLASM 



The visible effects produced by the action of the acids alone 

 and when combined with salts afford some interesting contrasts. 

 Acids like acetic when used alone produce a rigidity of the cilia 

 accompanied by swelling and finally disintegration. The cell 

 body assumes a coarsely granular appearance just before the 

 cilia stop moving and the vacuoles grow large and rigid. Rifts 

 appear in the protoplasm due to the clumping of particles and the 

 consequent squeezing out of fluid. If the acid is more dilute 

 than the solutions used in the present experiments, the vacuoles 

 soon cease to pulsate and like the rest of the body swell enor- 

 mousl3^ The more concentrated the acid the less the swelling. 

 When salts are added, results vary with the concentration of the 

 salt. With the more dilute salt solutions there is a great swelling 

 followed by coagulation and death. In mixtures containing 

 slightly more salts the coagulation is greatly delayed or even pre- 

 vented altogether and the swelling is often quite as extreme as 

 in very dilute solutions of the acid alone. When still more 

 salt is added, coagulation is postponed and there is* no swelling, 

 but instead a definite shrinkage which with Paramecium may 

 amount to 50 per cent. With Euplotes it is difficult to measure 

 the shrinkage, although it shows plainly in a collapse and curling 



