CONTRIBUTIONS FROM THE ZOOLOGICAL, LABORATORY OP THE MLSEOM OP COMPARATIVE ZOOLOGY AT 



HARVARD COLLEGE. NO. 285. 



THE MOVEMENTS OF THE TENTACLES IN ACTINIANS^ 



G. H. PARKER 



ONE FIGURE 



The tentacles of actinians have long been declared to be capa- 

 ble of carrying out many of their normal activities even after 

 they have been cut from the body of the polyp to which they 

 belong. This pecuHarity, which was recorded apparently first by 

 von Heider (79, p. 248) and has since been noted by others 

 (Parker, '96; Wolff, '04; Chester, '12), has been accepted as evi- 

 dence that each tentacle contained a neuromuscular mechanism 

 sufficient for its own activity and that it is therefore not depend- 

 ent upon the nervous control of other parts of the animal's body 

 for the production of those movements that it ordinarily exhibits. 

 To test the vahdity of this view, which has recently been ques- 

 tioned by Rand ('15, p. 208), was the object of the studies re- 

 corded on the following pages* 



The work was carried out on Metridium marginatum Milne- 

 Edwards, and Sagartia luciae Verrill at Woods Hole, Massachu- 

 setts, and on Condylactis passiflora Duch. and Mich, at Ber- 

 muda. The advantage of Condylactis for this kind of work is 

 evident because of the large size of its tentacles, and almost all 

 of the experiments recorded on the following pages were per- 

 formed on this species. 



In a full-grown Condylactis the oral disc may measure as 

 much as 12 cm. in diameter and carry as many as a hundred 

 tentacles. About half of these are near the outer edge of the 

 disc and the remainder are scattered toward the mouth. The 

 mouth is central in position, usually diglyphic, and partly cov- 

 ered by folds of the peristome. 



Each tentacle is from 12 to 15 cm. long, with a diameter of 

 about 1.5 cm. at its base and terminates distally in a blunt end 

 in which there is a pore. The tentacles are Ught brown in color 



1 Contributions from the Bermuda Biological Station for Research. No. 54. 



95 



