THE BEHAVIOR OF INFUSORIA; PARAMECIUM 



75 



Certain authors (Dale, 1901, Statkewitsch, 1903 a) have reported that 

 Paramecia sometimes swim with the current. But in these cases ir- 

 regular currents have been used, such as are produced by stirring the 

 water containing the animals. Using a tube, the present author has 

 found the results to be practically uniform, the animals swimming up 

 stream. If the reverse reaction actually occurs at times, it must be due 

 to some change of internal condition, such as results in swimming back- 

 ward under certain circumstances ; the direction of the current over the 

 body would be the same in the two cases. 



If the explanation of the reaction to water currents above given is 

 correct, this reaction is clearly analogous to the compensatory move- 

 ments of higher animals, as Lyon (1904) has brought out for other 

 organisms. It is a response to unusual relations with the environment, 

 and tends to restore the usual relations. 



B. Reactions to Gravity 



In the reaction to gravity the animals place themselves with anterior 

 end directed upward, and as a result swim to the top of the vessel con- 

 taining them, forming a collection there (Fig. 56). If the 

 tube is inverted after the collection is formed, so that the 

 infusoria are now at the bottom, they again direct the ante- 

 rior end upward, and swim to the top. These results follow 

 in the same way whether the upper end of the tube is open 

 or closed, and they take place equally well when the 



temperature is kept uniform 

 by immersing the tube in 



— 3C runn i n § water. 



To determine the way 

 in which the reaction oc- 

 curs, it is necessary to direct 

 the lenses of a microscope 

 of long focus upon a region 

 where the animals are tak- 

 ing up the position with long 

 axis in the direction of 

 gravity. 



KU 



Fig. 57. — Tube used in observing 

 the way in which Paramecium reacts to 

 gravity. 



Fig. 56. — 

 Paramecia col- 



This may best be lected at the top 

 accomplished by placing the ° 



tube, after Jen- 



animals in a U-shaped tube, sen (1893). 

 at first with the free ends upward. After the animals have become 

 grouped at the two free ends, the tube is inverted (Fig. 57). The 

 Paramecia now move upward, reach the cross-piece of the U, and 



