92 COMPARATIVE PHYSIOLOGY OF THE BRAIN 



the same case for a long- time. If the supracesopha- 

 geal ganglion (o, Fig. 26) be removed, the animal be- 

 comes restless, as S. S. Maxwell has found. It crawls 

 about on the sand unceasingly, making no attempt to 

 burrow. This restlessness is marked by one feature 

 which we find in higher animals after certain injuries 

 to the brain- -namely, the Nereis does not withdraw 

 from obstacles but attempts to force its way through 

 them. 



If normal Nereis are in a square aquarium the bot- 

 tom of which is covered with sand, they will crawl 

 about, if undisturbed, on the sides of the glass. This 

 is the result of stereotropism. A Nereis that has lost 

 the supracesophageal ganglion will behave in the 

 same way, except that when it reaches a corner it 

 does not turn out but attempts to go through the 

 glass. If there are several animals which have been 

 operated upon in a vessel, they will assume the po- 

 sition represented in Fig. 29. The worms remained 

 like this for many hours at a time, and then died in 

 consequence of their vain attempt to go forward. 

 Those reactions are wanting which in the normal 

 Nereis result from the application of contact-stimuli 

 to the oral end. The reader who is familiar with 

 brain-physiology may already have been reminded in 

 this connection of the dogs from which Goltz re- 

 moved the anterior half of the cerebral hemispheres. 



If glass tubes 20 cm. long, with a bore a little 

 larger than the diameter of the worm, are placed in 

 an aquarium without sand, the normal Nereis will 



