CARPENTER. — FEEDING REACTIONS OF THE ROSE CORAL. 153 



polyps kept in the laboratory become expanded, and may be experi- 

 mented upon in diffuse artificial light. If exposed to the direct rays of 

 an acetylene bicycle lamp the tentacles contract after a few minutes, but 

 they remain extended in diffuse light of sufficient intensity to render 

 them clearly visible to the observer. 



When the knob-like extremity of a tentacle is touched with a splinter 

 of wood the latter immediately becomes affixed to the end of the tenta- 

 cle, which is known to be loaded with nematocysts. Possibly the wood 

 is empaled by the numerous nematocyst threads, or it may be held by 

 some adhesive substance. However this may be, the splinter becomes 

 so securely fastened that considerable force is needed to pull it away. 

 A tentacle will often be drawn out two or three times its own length 

 before the splinter is freed, and I have sometimes feared it would be 

 torn from the body in the operation. 



If an expanded tentacle is touched on one side with the splinter, there 

 is a quick muscular response to the contact stimulus. The tentacle 

 immediately bends in the direction of the stimulating object, which it 

 affixes to the terminal knob. 



Similar results follow the use of a bit of filter paper in place of the 

 splinter, but if the paper is first dipped in meat extract, in addition to 

 the tentacular reaction the oral disk begins to sink and the edge zone 

 to fold over. In this reflex the distance of the receptor (the end of the 

 tentacle) from the effector (the endodermal body muscles) is worthy of 

 note. 



Action of 'the Cilia. Both the oral disk and the edge zone are abun- 

 dantly provided with cilia. Carmine particles dropped anywhere on 

 their surfaces are rapidly transferred to the outer margin of the polyp, 

 showing that the usual beat of the cilia is toward the periphery. Car- 

 mine particles dropped at the very margin of the mouth pass immedi- 

 ately into the stomodteum, the cilia of which appear to beat constantly 

 inward. 



When carmine grains which have previously been soaked in meat 

 extract are dropped on the oral disk they also are usually carried to 

 the peripheral margin of the polyj), even though the stimulation of the 

 nutrient material may be sufficient to cause a slow sinking of the oral 

 surface. I repeated this experiment many times with different polyps, 

 and occasionally succeeded in obtaining a reversal of the cilia, which 

 caused the carmine grains to move toward, and not away from, the 

 mouth. I was, however, unable to obtain consistent reactions, and 

 never could predict what the result would be. Analyses of the brand 

 of meat extract used (Liebig's) indicate that it contains several of the 

 substances shown by Parker (:05* and :05'') to be the effective stimuli 



