MOVEMENTS OF TENTACLES IN ACTINIANS 105 



tacle any nervous system whatever. It has been pointed out 

 elsewhere (Parker and Titus, '16) that the histological evidence 

 for this layer is by no means conclusive and the physiological 

 evidence as thus far elicted from Condylactis is entirely op- 

 posed to a belief in its presence. In only one point do I find 

 anything in the physiology of the tentacular entoderm that is 

 suggestive of a contained nervous system. It has already been 

 observed by Rand ('09, '15) that when a tentacle of Condy- 

 lactis is cut off, the stump closes through the action of the cir- 

 cular muscles, whereby a nipple is formed. This closure does 

 not occur in tentacles anesthetized by chloretone. I have 

 elsewhere shown that chloretone will not check the action of 

 the muscles in the acontia, though it is very effective as a narco- 

 tizer for the neuromuscular mechanism proper. I therefore be- 

 lieve that in actinians it directly effects nervous action and 

 that its influence on muscle alone must be of an indirect 

 kind. The narcotization of a tentacle must abolish this indi- 

 rect influence, though I cannot say whether or not this involves 

 some slight nervous activity. Aside from this I have been 

 unable to get any evidence that the entoderm of the tentacle of 

 Condylactis contains nervous elements. If such elements are 

 present, they must be of a very primitive kind and certainly 

 much less effective than thpse in the ectoderm, for the circular , 

 muscle fibers never react quickly and seldom respond as a 

 whole in the way that the longitudinal muscle does, but much 

 more usually in a local fashion, whereby rings of constriction are 

 formed as in tentacular autotomy and other such spincter-like 

 activities. 



A good example of the different action of these two muscles 

 is seen in the following experiment. If a suspended tentacle 

 filled in the usual way with seawater is vigorously stimulated 

 mechanically at one point, the whole tentacle instantly con- 

 tracts. On being refilled it reexpands in a few minutes except 

 for a marked circular constriction in the region stimulated; this 

 then gradually disappears. Thus the quick action of the longi- 

 tudinal muscle and the slow action of the circular muscle 

 is well demonstrated. If, now, the experiment is repeated but 



