MOMOGRAPH OF THE EXISTTNG CRINOIDS. 697 



prolongations, and the arms. A needle was then passed down the canal included 

 in the radials so as to irritate the chambered organ. 



All the 10 arms then suddenly and consentancdusly closed up. On the with- 

 drawal of the needle the arms gradiially straightened themselves again, and again 

 coiled up as before when the irritation of the central organ was renewed. 



Dr. Carl F. Jickeli, working with Antedon adriatica at Trieste, performed 

 some experiments along the same lines as those of Doctor Carpenter. These were 

 as follows : 



Exferiment 1. — If a freshly amputated ann, or an amputated arm even which 

 has lain a few days in sea water, be scratched with a needle on the ambulacral 

 groove, or its ambulacral groove be subjected to electrical stimulation, no raising 

 of the pinnules can be detected. But as soon as the cavity in the brachial contain- 

 ing the dorsal cord is touched the arm coils up convulsively and the pinnules are 

 set in active motion, even when previously no signs of life could be detected 

 in the arm. 



Experiment 2. — If the ambulacral groove be scraped away, or burned away 

 with caustic, reaction can always be obtained to the touch of a needle in the 

 central canal. But if the central canal be burned out with caustic the arm is 

 stretched out stiffly and all further stimulus is in vain. 



Experiment S. — If a detached cirrus be jiricked in the central canal, or if the 

 central canal be stimulated with an electric current, the cirrus is violently bent and 

 a state of tetanus sets in. 



Experiment 4. — If an animal be deprived of the visceral mass and put back 

 into the water, ventral side up, all the arms are rigidly stretched out. If, now. a 

 needle is thrust into the centrodorsal from the ventral side all the arms bend 

 together synchronously, and again sink back into their original position. If a few 

 drops of acid are added to the water the animal immediately begins to swim about 

 witli great activity, the movements agreeing entirely with those of \minjured 

 animals. 



Prof. A. Milnes Marshall, in confirmation and amplification of Carpenter's 

 results, performed a number of experiments, his subject being Antedon mcditer- 

 i-anea, which he studied at Naples. 



Experiment 1. — A large and vigorous specimen was eviscerated without re- 

 moval from the water. On being released it remained quiescent for about a minute, 

 and then swam about the tank actively and in a perfectly normal manner. After 

 a short time it came to rest on the bottom in a perfectly normal position. Half 

 an hour later, without the slightest disturbance or irritation of any Idnd, it began 

 spontaneously to swim again, actively and normally. Coming in contact with a 

 piece of stick, it attached itself to it by the dorsal cirri, and remained there for 

 more than a week. 



Experiment 2. — An active specimen was eviscerated and allowed to come to 

 rest. The ventral surface of one of the arms was then irritated gently with a needle. 

 Active movements both of the irritated arm and of the others resulted. The same 



