40 TROPISMS 



have the same orientation as the cell bodies which send 

 their fibers to the extensors of the fifth pair of legs 

 (Fig, 8). Hence when the positive current goes from 

 head to tail through the animal (Fig. 8), the flexors of 

 the third pair of legs and the extensors of the fifth pair 

 must be thrown into greater activity, since the cell bodies 

 of both these nerves are in a condition of catelectrotonus, 

 i.e., increased activity. 



Fio. 8. Fio. 9. 



FIGS. 8 and 9. Diagram indicating orientation of neurons for flexor and extensor 

 muscles of third and fifth pairs of legs to explain galvanotropic reaction. (After Loeb 

 and Maxwell.) 



When the current goes from tail to head the cell bodies 

 of the extensors of the third and of the flexors of the fifth 

 pair of legs are in catelectrotonus. This possibility is 

 expressed in the diagram Fig. 9. 



In this way the theory of the galvanotropic reaction 

 of those animals which go to the anode seems complete. 



What has been demonstrated for Palcemonetes holds 

 not only for many crustaceans but for vertebrates also. 

 Loeb and Garrey 306 have shown that when a current 



