MOVEMENTS OF TENTACLES IN ACTINIANS 



99 



responsive. But I failed in devising any technique by which 

 the root of the tentacle could be rendered insensitive and the 

 distal part left unaffected. 



I. therefore turned to methods of procedure that were least 

 disturbing to the normal tentacles. The best of these consisted 

 in holding at the surface of the sea-water a quiescent severed 

 tentacle by means of a minute hook made by bending shghtly 

 the pointed end of an entomological pin (fig. 1). Into the open 

 end of such a suspended tentacle sea-water could be run from a 

 glass pipette and thus the tentacle could be brought to a reason- 



Fig. 1 



able degree of distension. Such severed tentacles when first put 

 on the hook were contracted to about one-third their normal 

 length. As their condition did not differ essentially from that 

 of loosely floating severed tentacles, I concluded that the effect 

 of the hook was negligible. On discharging water into them they 

 gradually expanded till they were about two-thirds as long as 

 they were before their separation from the polyp. They ex- 

 hibited moreover just about that degree of distension and mo- 

 bility that was seen in the attached tentacles. If, now, more 

 water was discharged into them, they were very likely to elongate 

 a little and then contract considerably discharging much of the 

 contained water. This response confirms the opinion already 



