Implications of the Theories of Nerve Action 193 



tion that the brain is a fundamentally originative and coor- 

 dinative member. For example, an individual thus depleted 

 will crawl about unceasingly on the sand of the aquarium 

 bottom, without, however, showing any signs of burrowing 

 into the sand, though this operation is very characteristic 

 of the normal animal. This looks as if the brain were indeed 

 the seat of the burrowing instinct. But not so. The bur- 

 rowing activity can be induced not only in animals deprived 

 of the brain, but even in parts of animals from which the 

 heads have been cut away altogether. Loeb placed a brain- 

 less piece of a Nereis on the sand, and as usual it remained 

 quiet. "I then gradually covered the forward end with 

 sand. The rest of the animal immediately began to make 

 the typical movements which the animal makes in forcing its 

 way into the sand. At the same time the glands began to 

 secrete the sticky substance which cements the particles 

 of sand together, forming the wall of the burrow-hole." 

 "But, why," Loeb asks, "does the Nereis not burrow when 

 deprived of its brain? For the simple reason that it makes 

 use of the organs of the mouth in burrowing, and these are 

 amputated with the head. Hence it is the loss of the pe- 

 ripheral head-organs which keeps the decapitated Nereis from 

 burrowing, and not the loss of the brain." 



Since the coordinated activities involved in burrowing can 

 be accomplished through the acting together of various su- 

 perficial and deeper body parts sense organs, muscles, and 

 so on without the intermediation of the brain, these pe- 

 ripheral members are the real "seat" of such activities. The 

 author then goes on to inquire what part the brain does play 

 in the creature's normal life. "If we compare," he says, 

 "the conduct of a Nereis whose brain has been amputated 

 with that of a normal worm, the difference seems to be of the 

 same nature as that between an insane and a rational human 

 being. . . . The peculiar irritability by means of which the 

 Nereis draws its head back and moves backward out of the 



