280 PROFESSOB MARSHALL. 



The experiments prove in the most positive manner that the central 

 capsule is in direct physiological connection with the muscles of the 

 arms; and the further fact that the experiments yield identical results, 

 •whether performed on eviscerated or unmutilated specimens, proves 

 that the subepithelial bands form at any rate no part of the central 

 mechanism. 



Experiment 7. — The centrodorsal plate of an active specimen was 

 removed with scissors and the central capsule carefully scooped out 

 with a small scalpel. The animal on being released fell to the bottom 

 of the water, where it lay on its side with the arms very strongly 

 extended ; it remained in this position for several hours without any 

 attempt to move. If taken from the water and thrown in again the 

 arms moved fairly actively, but there was no attempt at swimming, 

 each arm apparently acting quite independently of the rest. Finally, 

 if placed on its oral surface it remained there for an indefinite time 

 without making the slightest attempt to right itself. 



Experiment 8. — The preceding experiment was repeated on an 

 eviscerated specimen, the results being in all respects the same. 



These two experiments are of very great importance. They show 

 that removal of the central capsule completely destroys the co- 

 ordinating mechanism between the arms, as tested (a) by the power of 

 executing the normal swimming movements, (b) by the power of 

 righting itself when inverted ; both these powers being permanently 

 destroyed by the operation. To obtain definite results it is necessary to 

 completely remove the central capsule, and this I have found cannot be 

 effected by simply cutting aw*ay the centrodorsal plate ; besides this the 

 capsule must be either scraped out with a fine scalpel or else destroyed 

 by free painting with strong acid. Specimens in which the centrodorsal 

 plate has been simply snipped off, though they lose temporarily the 

 power both of swimming and of righting themselves, yet regain these 

 more or less completely after an interval of half an hour to an hour. 

 If, however, sufficient care has been taken to entirely destroy the 

 central capsule the loss of power is absolute and permanent. 



Experiment 9. — The centrodorsal plate of an active specimen was 

 removed, and the central capsule entirely destroyed ; the cavity was 

 also very freely painted with nitric acid so as to expose and destroy 

 the pentagonal commissure connecting the axial cords together at their 

 roots (cf. fig. 3). After being left at rest for an hour the arms were 

 irritated one by one ; each arm responded readily and extensively to 



