470 G. H. PARKER 



irregularity of the courses of the convolutions I was unable to 

 determine the sense of the direction in their sweep. On the 

 acontia the cilia beat persistently toward the free end of these 

 organs, as already described by Torrey ('04, p. 214). 



Excepting for the matter of reversal, there is nothing in the 

 action of the cilia of Metridium, or in fact of those of other acti^ 

 nians, that would lead to the suspicion that these organoids 

 are under nervous influence; and in those that reverse their 

 effective stroke the reversal is so strictly local in reference to 

 the stimulus that no nervous interpretation of this special activity 

 is suggested (Parker, '96, p. 114). The same strict agreement 

 in the localization of stimulus and area of reversal has been 

 pointed out by Duerden ('06, p. 596) for the coral Fungia, indi- 

 cating that in this group also the ciliary reversal is probably 

 non-nervous. 



Not only does agreement in the distribution of stimulus and 

 of response favor a non-nervous interpretation of ciliary action 

 in actinians, but experiments with anaesthetics also support 

 this view. If a Metridium whose labial cilia have been shown 

 to reverse to meat, is placed quickly in a large volume of sea- 

 water containing some chloretone and allowed to remain there 

 for five minutes, all traces of neuromuscular activity will dis- 

 appear, though ciliary reversal will still occur with great pre- 

 cision. The reversal also takes place in a perfectly clear and 

 indisputable manner in animals that have been anaesthetized 

 with magnesium sulphate. Since these two substances complete- 

 ly abolish neuromuscular activity and yet interfere in no essen- 

 tial way with the ciliary reversal and other like activities in 

 Metridium, it is safe to conclude that the cilia of this and other 

 actinians, unlike the swimming plates in ctenophores, are quite 

 independent of nervous control and in this respect are like the 

 cilia in higher animals. In this particular, then, the ciliary 

 system in Metridium is like the mucous system, and the nema- 

 tocyst system in this animal, an effector mechanism independent 

 of nervous control. 



