NERVOUS SYSTEM OF ANTEDON EOSACEUS. 533 



Experiment 14. — An active specimen was removed from 

 the water, the dorsal surface of one of the arms carefully dried, 

 and strong nitric acid applied with a fine brush to the dorsal 

 surface of the sixth and seventh radials, which were dissolved 

 away until the axial cord was exposed and destroyed. If the 

 arm were held during the operation it was usually thrown oflF, 

 but if the disc only were held and the arm allowed merely to 

 rest on the fingers, the operation was always successful. The 

 animal was then returned to the water, where it assumed 

 almost at once the normal position. After half an hour's rest, 

 the distal end of the injured arm was nipped sharply with for- 

 ceps; active movements of the irritated arm beyond the injury 

 ensued, but no movement whatever of either the proximal part 

 of the injured arm or of any of the other arms. 



This experiment also was repeated several times on both 

 entire and eviscerated specimens, the results being without 

 exception as recorded above. It is diflicult to limit the action 

 of the acid to the dorsal surface of the arm, but by sufficient 

 care it can be done, and on several occasions the ambulacral 

 epithelium, including of course the subepithelial band, was left 

 absolutely uninjured, responding to stimulation in a perfectly 

 normal manner. The experiment must, I think, be considered, 

 when taken in conjunction with Experiment 13, as proving that 

 the axial cord is the sole afi'erent communication between the 

 arm and the central motor mechanism, for the former experi- 

 ment shows that the communication is still perfect when it 

 alone remains, while the latter shows that division of the cord, 

 other parts remaining intact, destroys the communication 

 absolutely. 



Experiment 15. — One further and very obvious experi- 

 ment is worth recording. One of the arms of an active speci- 

 men was cut across about its middle, and the animal held in 

 the tank so that the stump of the amputated arm was just 

 above the surface of the water ; the cut end of the axial cord 

 could then be very readily seen with the naked eye. The 



