Nervous System of Jelly-fish 49 



to clearly show that, when definite parts of its 

 sensitive surface are appropriately stimulated, 

 its body-substance responds by well-ordered 

 and distinctly purposive movements, that is to 

 say, by instinctive behaviour calculated to pro- 

 mote the well-being of the animal and the 

 species to which it belongs. When the entire 

 margin of the bell of a living jelly-fish, in- 

 cluding therefore the whole of its sensory 

 organs and system of nerve cells is excised, 

 neither mechanical nor any other form of 

 energy applied to the remaining part of the 

 bell produces any movement in it or in the 

 manubrium. In place of excising the margin 

 of the bell, Romanes made an incision above 

 the situation of its nerve cells, parallel to its 

 margin. Under these conditions the move- 

 ments of the manubrium became uncertain ; it 

 no longer bent down to the seat of irritation, 

 but dodged about from one to another part of 

 the margin of the bell; it had seemingly lost 

 its power of localising the spot irritated. 1 The 

 manubrium, under these conditions, being acted 



1 Jelly-fish, Star-fish, and Sea-urchins, by G. F. Romanes, 

 P- 33- 



