88 



BEHAVIOR OF THE LOWER ORGANISMS 





single electric shocks the animals react more strongly when the anterior 

 end is directed toward the anode. Often there is no reaction when they 

 are in the opposite position. Consider a specimen that is oblique, as in 

 Fig. 63, b'. The current comes alternately from the right and left. To 



the current coming from the left 

 (anode at the left) the Paramecium 

 reacts strongly, since its anterior end 

 is directed toward the anode. It 

 therefore turns its anterior end in the 

 opposite direction, to the right. 

 To the opposite current, on the other 

 hand, it reacts little or not at all, 

 since the anterior end is not directed 

 toward the anode. Continuing thus 

 to react to the repeated currents from 

 the left, it must come into the trans- 

 verse position. Here the anterior end 

 has the same relation to both currents ; 

 hence it swings as far to one side as to 

 the other. Since it changes its posi- 

 tion very little at any one reversal, it 

 maintains on the whole the transverse 

 position. 



FIG. 64. Positions taken by Para- 



mecia in rapidly reversed currents, a, Posi- Under a Constant Current in One 



tions in weak currents, or in moderate direction, the general effect of the 

 currents at the beginning of the experiment. ...... 



c and d, Positions taken in stronger cur- behavior IS of COUrSC to CaUSC the ani- 

 rents, or after the experiment has lasted for ma ls to pass to fa e ca thode. Here theV 

 some time. After Statkewitsch (1903 a). . . 



may gather in a dense mass. But if 



the cathode is so placed that the Paramecia can pass behind it, they do 

 this, thus reaching a region where the current is not acting (Fig. 59, 

 B). Here they swim about in all directions. If one comes by chance 

 again into the field of the current, it is at once returned, by the usual 

 reaction, to the region behind the cathode. If in any other way certain 

 areas are left free from the action of the current or with very little cur- 

 rent, the animals gather in these free areas. Birukoff (1899) has de- 

 scribed and figured many such cases, produced under induction shocks 

 by the aid of electrodes of different forms ; his results have been extended 

 by Statkewitsch (1903 a). 



It is evident that the reaction to the electric current differs funda- 

 mentally from the known behavior under other classes of stimuli. Under 

 other stimuli the movements are coordinated, all tending toward the same 

 end, while in the electric current different parts of the body oppose each 



MAW, 



