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 slightly 

 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 



