MORPHOLOGY AND BIOLOGY. 21 



If an amoeba in which several pseudopodia are 

 present is gently touched with a needle upon only one 

 of the pseudopodia, they are all quickly withdrawn, 

 thus proving that the protoplasm of the organism 

 possesses conductivity. 



MOTILITY. Aside from reproduction, the most 

 striking phenomenon observed in amoeba? is the power 

 of locomotion. This is rendered possible by a form 

 of motility which, because it is best illustrated in 

 amoebae, is known as amoeboid motion. This, the most 

 primitive form of locomotion, consists in the throw- 

 ing out of pseudopodia at the periphery of the 

 organism and the flowing into them of the cytoplasm. 

 Jennings compares it to rolling, the upper surface 

 of the cytoplasm passing forward and turning under 

 at the anterior end of the pseudopodia, thus produc- 

 ing the appearance of the cytoplasm flowing in the 

 direction of motion. By this means an amoeba is able 

 to move in any direction, the rate of rapidity of 

 motion varying with the surroundings and the species 

 of organism. Locomotion in any one direction only 

 lasts for a short period of time, and it is not unusual 

 to observe an amoeba move in the opposite direction 

 without any apparent reason. When an obstacle is 

 encountered by a pseudopodium it is quickly with- 

 drawn and another is protruded, the organism mov- 

 ing away in another direction. 



