Jennings, Behavior of Paramechan. 4gg 



to the fact that Roesle used no method of rendering the cur- 

 rents visible. When the circuit is closed with the peristome to 

 the anode, on the other hand, the oral cilia strike strongly 

 backward, and this has a powerful locomotor effect, driving the 

 animal forward, or, if the current continues, turning it toward 

 the aboral side. Roesle's observations are then fully explica- 

 ble on the basis of the known action of the current on the cilia, 

 as described first by Ludloff, together with the stronger loco- 

 motor effect of the oral cilia when striking backward, a difference 

 that is evident in many ways. I must then agree with the con- 

 clusion of Statkewitsch (1903), reached on other grounds, 

 that the results of Roesle do not demonstrate the greater sen- 

 sitiveness of the peristome. 



Thus we find under certain circumstances a "transverse 

 electrotaxis" of Paramecium under the action of the constant 

 current, as in many other infusoria. This transv/erse orienta- 

 tion is of course of an entirely different character from that ob- 

 tained by Statkewitsch (1903 a, pp. 24-32), with rapidly 

 alternating currents. 



3. In a strong electric current the contact reaction causes 

 not merely a stoppage of the forward course, but actual swim- 

 ming backward. If the Paramecia are in a thin layer of water, 

 through which a rather strong current is passed, all the speci- 

 mens that are not in contact with upper and lower surfaces 

 swim forward, in the somewhat cramped manner, as if against 

 resistance, that is characteristic of the swimming in a strong 

 current. But when a specimen comes in contact with the glass 

 surface below or the surface film above, it begins to swim back- 

 ward. This may last for but an instant, while the accidental 

 contact continues, or if the animal remains in contact the back- 

 ward swimming continues a long time. If a very thin layer of 

 water is used, so that the Paramecia can hardly avoid coming 

 in contact with a surface, most of them swim backward, though 

 as soon as a specimen becomes free from the surface, it darts 

 forward. With a slightly thicker layer of water, often about 

 half the individuals are free and swim forward, while the other 

 half are in contact and swim backward. The same individual 



