THE NERVOUS SYSTEM OF ANTEDON ROSACEUS. 279 



ease with which this extensive regeneration is effected in Antedon 

 would certainly be still more surprising were the main centre of the 

 nervous system to be lodged in the part lost, and so far may be 

 regarded as an argument against such a location. 



D. On the Functions of the Central Capsule. 



Experiment 4. — A specimen was eviscerated and allowed to come to 

 rest ; a needle was then passed from the oral surface down the canal 

 surrounded by the First Eadials (fig. 1) so as to irritate the central 

 capsule ; the result was immediate flexion of the arms, and in many 

 cases active swimming movements of the whole animal. 



Experiment 5. — A specimen was eviscerated and then cut into two 

 parts, one having two pairs of arms and the other three. The central 

 capsule, which was divided and freely exposed by the operation, was 

 then irritated by a needle. The slightest irritation caused very active 

 and violent flexion of the arms. 



Experiment 6. — An active uninjured specimen was held under water, 

 and the dorsal half of the centrodorsal plate removed by a single snip 

 with a large pair of scissors so as to expose and partly remove the 

 central capsule (cf. fig. 1). On being released the animal fell to the 

 bottom with the arms very strongly extended, but in about twenty 

 minutes gradually righted itself and assumed the normal position. 

 The exposed central capsule was then irritated, first with a needle and 

 then with strong nitric acid applied by a small brush ; the effect of 

 irritation was to cause very strong and spasmodic flexion of the arms, 

 which in the first case ceased on removal of the stimulus, but in the 

 case of the acid persisted for several hours. 



The three preceding experiments show that irritation of the central 

 capsule, whether mechanical or chemical, causes strong flexion of all 

 the arms, which persists as long as the stimulation is continued. 

 Experiment 4 is the same as Dr. Carpenter's Experiment A, though 

 the results are not quite identical ; for while Dr. Carpenter describes 

 sudden and consentaneous flexion of the arms as following irritation 

 of the central capsule from the oral surface, I have found that 

 swimming movements quite as often result. The difference is a 

 slight one, and may, I believe, be accounted for by the oral pinnules 

 being accidently irritated in some of the experiments. If these were 

 clipped off I found that swimming movements of the arms almost 

 invariably followed irritation of the central capsule from above. 



