i56 



BEHAVIOR OF THE LOWER ORGANISMS 



(4) If Colpidium is squarely transverse, with oral side to the cathode 

 (Fig. 104, 1), or especially if the anterior end is a little inclined toward 



the anode, the organism often starts trans- 

 versely to the current. Suddenly it jerks its 

 body a little toward the aboral side (Fig. 

 104,1-2), then moves forward again. Again it 

 jerks toward the aboral side (3), again moves 

 forward, and repeats this behavior until the 

 anterior end is directed toward the anode. 

 Then it turns steadily toward the aboral side 

 till the anterior end is directed toward the 

 cathode (Fig. 104, 4-5). In this behavior the 

 two tendencies mentioned oppose each other, 

 as in case 2, but the second one prevails over 

 the first. 



Various combinations of these different 

 reaction types may occur, making the be- 

 havior of Colpidium under the electric cur- 

 rent very complicated. Similarly varied be- 



— 



Fig. 104. — Another method 



of reaction to the electric current havior is often observed in other infusoria, 



in Colpidium. After Pearl through the action of similar causes. 

 (1900). 



as 



In such 



+ 



infusoria as Stentor, where the 

 peristomal cilia form a circle surrounding the anterior end, there is no 

 reason for such a conflict of tendencies. The peristomal cilia are 

 divided by an electric current coming from one side, so that the ani- 

 mal turns directly away from the side on which these 

 cilia strike backward (Fig. 105). If the anterior end 

 is directed toward the anode at the beginning, the 

 animal doubtless turns as usual toward the right 

 aboral side. In other positions the usual method of 

 turning seems to have no effect on the reactions. In 

 Vorticella and other infusorians resembling Stentor 

 in the distribution of the cilia, the orientation to the 

 current would doubtless take place in the same direct 

 manner, though this has never been determined. 



In Spirostomum and Opalina, the conflict of the 

 two tendencies mentioned above leads to certain very 

 remarkable and complex results. Under usual con- 

 ditions Spirostomum takes a transverse position in 

 the electric current, while Opalina swims to the 

 anode. The gross features of the behavior thus differ 

 markedly from those shown by most other infusoria. 



Fig. 105. — Re- 

 action of Stentor when 

 transverse to the cur- 

 rent. It turns directly 

 toward the cathode, 

 all the cilia concur- 

 ring to produce this 

 effect. 



