A 



A 



TRANSMISSION IN THE NERVE-NET 131 



lated, the whole tentacle is likely to respond, but when a 

 point lower down on the side of the tentacle is stimulated, 

 the reaction is chiefly from this point proximally ; in other 

 words, transmission is more readily accomplished from 

 the tip toward the base of the ten- 

 tacle than in the reverse direction. 

 The same kind of evidence has 

 been shown by Rand (1909) to 

 come from the reparative steps in 

 regeneration. If a tentacle is cut 

 off, the stump contracts vigorously 

 and on reexpanding forms a ter- 

 minal nipple; the cut face of the 

 distal segment usually contracts 

 only a little and seldom, if ever, 

 closes the open wound. Yet, if such 

 a distal piece is again cut cross- 

 wise, its proximal part contracts 

 and eventually forms a nipple, 

 while the distal piece remains al- 

 most unaffected (Fig. 38). The 

 polarity thus exhibited is in the 

 same direction as that which was 

 shown by the reactions of the at- 

 tached tentacle to mechanical 

 stimulation. 



If the tentacles of a sea-anemone that has been thor- 

 oughly anesthetized with chloretone are touched, no re- 

 sponse whatever follows. If they are cut, neither the 

 proximal nor the distal parts contract but both remain 

 flabbily open. In consequence of these conditions it is 

 believed that the polarity of the tentacle in so far as it 

 is exhibited by the reaction just noted is of a nervous na- 



A B 



FIG. 38. Diagram of the 

 reactions of a tentacle of a 

 sea-anemone to transection. 

 On transecting a tentacle A , the 

 distal end of the proximal 

 piece a contracts and forms a 

 nipple and the proximal end of 

 the distal piece 6 remains open. 

 On transecting the distal piece 

 B the process is repeated in 

 that the distal end of the new 

 proximal piece c forms a nip- 

 ple and the proximal end of 

 the new distal piece d remains 

 open. 



