108 G. H. PARKER 



cLilar cavity of the animal (Jordan, '07), the transmitted pres- 

 sure and the moderate inflow of nervous impulses are the only 

 significant contributions of the whole animal to the tentacle. 

 Yet, as the experiments already described show, neither of these 

 are really essential to the responses of the tentacle, whose activi- 

 ties can be carried out by its own neuromuscular mechanism. 

 How striking this condition is, can be made plain if the coordi- 

 nated efficiency of an actinian's tentacle after separation from 

 the body is compared with the state of an amputated appendage 

 from an arthropod or a vertebrate. In the latter practically all 

 traces of spontaneous movement and coordination have disap- 

 peared and only spasmodic jerks can be called forth by vigorous 

 stimulation. Whereas in the former the range of response and 

 the coordination of the individual acts differ from those of a 

 normal animal, as has already been shown, only through slight 

 operative disturbances. In seeking among the organs of the 

 higher forms for a parallel to the actinian tentacle, one is con- 

 tinually reminded of the vertebrate heart, whose essential ac- 

 tivity is so shghtly interfered with even by removal from the 

 body. The similarity in the action of the heart and of the ten- 

 tacle under these circumstances is due to the fact that each pos- 

 sesses within its own substance a neuromuscular mechanism es- 

 sentially independent of the rest of the body. The same is true 

 of the separate arms of certain starfishes, which may move about 

 as independent organisms before they have regenerated their de- 

 ficiencies. Nor is the tentacle of the sea-anemone the only or- 

 gan in this animal that exhibits organic independence of the 

 kind already described. As will be shown in a subsequent paper, 

 the pedal disc of the actinian when separated from the oral disc 

 may creep about for a long time with well coordinated locomotor 

 waves. This example, as well as others that might be cited from 

 the actinians, as for instance the acontia, show the great inde- 

 pendence of the parts of these animals in contrast with those in 

 most other forms. To be sure, an actinian tentacle has never 

 been known to regenerate a new individual and in this respect 

 the tentacle is a totally subordinate organ, but in the direction 

 already indicated it exhibits most remarkable independence and 



