276 PROFESSOR MARSHALL. 



others, so as to slightly lift the disc on that side, the pinnules of the 

 flexed arm being extended and apparently used to push against the 

 ground. Then after another pause, a rather sudden and violent flexion 

 of the arms immediately adjacent to the already flexed one causes the 

 animal to turn on its side, when a few energetic swimming movements 

 place it right way up. An active animal has apparently the strongest 

 objection to being placed mouth downwards, and will right itself again 

 and again if so inverted. When attached by the cirri, however, they 

 may, as noticed above, remain in the inverted position for days or weeks. 



If an arm be cut off from an active Antedon, the detached arm will 

 retain its vitality for many hours. It will at first exhibit strong 

 movements of flexion, lasting from a few minutes to as long as a 

 couple of hours, the arm. being alternately coiled up spirally, and then 

 extended with great force and rapidity. 



Antedon, if kept in captivity, requires the water to be frequently 

 changed, or else very efficiently aerated. Specimens left over-night 

 in a small basin of sea-water were found dead the next morning. In 

 dead specimens, owing to the unopposed action of the elastic ligaments, 

 the arms are very strongly extended. 



B. On the Effects of Removal of the Visceral Mass. 



In a living specimen the visceral mass can be removed from the 

 calyx with great ease, as was pointed out long ago by Dr. Carpenter. 

 If the visceral mass be grasped with forceps an exceedingly slight pull 

 suffices to remove it. In such eviscerated specimens the central capsule 

 with its prolongations and the axial cords remain in the calyx intact, 

 excepting, of course, the branches of the cords described by P. H. 

 Carpenter as distributed to the oral perisome : the ambulacral grooves 

 and other soft parts, on the other hand, are torn across at the 

 bases of the arms, and the subepithelial bands consequently isolated 

 from one another. 



Experiment I. 1 — A large and vigorous specimen- was eviscerated 

 without removal 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, 



1 For convenience of reference I propose to number the various experiments consecutively. 

 It will be understood that they were not made in the order given here, and that only those 

 which seem of distinct importance are recorded. No experiment is described from a single 

 observation only, and in most cases the experiments wore repeated several times. 



