NERVOUS SYSTEM OF ANTEDON EOSACEUS. 531 



Experiment 12. — An active specimen was taken, and all 

 the soft parts scraped away with a knife from the ventral 

 surface of one of the arms, the scraped portion being about a 

 quarter of an inch in length and one inch from the disc. The 

 pinnules were immediately folded closely alongside the wound, 

 and the animal on being released swam actively in a direction 

 away from the injured arm. It soon came to rest in the normal 

 position, and about six minutes after the operation the distal 

 end of the injured arm was nipped with the forceps. The 

 distal part of the arm, beyond the injury, was at once flexed 

 actively, the proximal part less actively, and the other arms did 

 not move. After a twenty minutes^ interval the distal end of 

 the injured arm was again nipped, when active movement of all 

 the arms at once resulted, the animal moving rapidly away 

 from the source of irritation. 



The above experiment shows that the communication between 

 the sensitive surface of an arm or pinnule and the motor 

 mechanism of all the arms is not effected by the subepithelial 

 band. The practically negative result obtained when the 

 stimulation was applied very shortly after the operation is, I 

 think, most certainly to be ascribed to the shock of the opera- 

 tion, which, as already noticed, must always be kept in mind 

 as a disturbing element. 



If the communication is not effected by the subepithelial 

 band, nor by any of the soft parts of the ventral surface of the 

 arm — all of which were scraped away in the operation — it must 

 take place either through the integument of the dorsal and 

 lateral surfaces of the arm, or through the calcareous segments, 

 or through the axial cords, for these are the only parts left 

 uninjured. To determine which of these is the real path of 

 communication the following crucial experiment was made. 



Experiment 13. — A large and vigorous specimen was taken, 

 aud a quarter of an inch of one of the arms, about an inch from 

 the base, thoroughly scraped with a scalpel all round so as to 

 remove the soft parts as completely as possible. The pinnules 



