Jennings, BeJiavior of Paratnecinm. 501 



incorrect. As to the first one, the Paramecia, as we have seen, 

 show the interference described even when the animal is in con- 

 tact only with a clean glass surface, or with the surface film of 

 the water. It is evident that this cannot be explained as due 

 to the dividing of the current and the passage of a weaker por- 

 tion through the object with which the animal is in contact. 

 Statkewitsch's observations on this phenomen (1903 a, pp. 

 45-52) were made only on individuals in contact with a bit of 

 detritus, and he assumes that this is a necessary condition for 

 the production of the supposed interference. 



As the second assumption mentioned, I have shown above 

 that the contact reaction produces not a mere weakening of the 

 effect of the electric current, but actual changes of a most de- 

 cided character in the way the reaction occurs. Paramecia 

 in contact with a glass surface or the surface film take up a 

 transverse position, or move backward, in the same current 

 which produces forward movement in free swimming specimens. 

 These effects cannot possibly be explained as due to the divid- 

 ing of the current into weaker and stronger portions, as sup- 

 posed by Statkewitsch. 



Putter (1900) had already set forth that in Stylonychia 

 the contact reaction has the effect of producing a transverse 

 orientation in the electric current. Statkewitsch, however, 

 tries to show that this transverse orientation is merely the effect 

 of a weak current. But when one examines attentively his 

 evidence for this (1903 a, pp. 43-44) it seems apparent that all 

 the specimens which showed transverse orientation were in con- 

 tact with a surface, and he does not mention the existence of 

 transverse orientation in free swimming specimens. Thus his 

 results are equally well explained on Putter's view that the 

 transverse orientation is due to the contact reaction. In Para- 

 mecium Statkewitsch expressly states repeatedly (for exam- 

 ple, 1903 a, p. 57) that the effect of the weak current is to cause 

 movement toward the cathode, and he never in his extensive 

 and thorough study of the reaction of Paramecium to electric- 

 ity observed transverse orientation to the constant current. The 

 transverse orientation of Paramecia that are in contact, described 



