CONDUCTIVITY 



123 



Fig. 15. 



Difflugia urceolata. A— Weak local stimulation at the end of a long extended pseudopod. 

 B— Stronger local stimulation applied to the end of a long pseudopod. 



last there is complete disappearance. (Figure 15, B.) The 

 pseudopod has at the same time retracted to a considerable 

 degree. If a still stronger stimulus is applied by firm pressure 

 at the end of the pseudopod the process takes place with much 

 greater violence. The differentiation of the protoplasm spreads 

 centripetally from the point of stimulation over the whole 

 pseudopod with great rapidity, and produces a quick retraction 

 in the same, then involves the oppositely directed pseudopod, 

 in which it then extends more and more slowly, until, proceeding 

 in a centrifugal direction, it is at last gradually completely oblit- 

 erated. When strong stimulation is applied, the process occurs 

 with such rapidity that the contraction of the pseudopod is 

 almost twitchlike. As the rapidity of the conduction alters 



