HYDEOIDS 191 



more easily those muscles that lie near the receptive po- 

 sition than those that lie far from it. 



Enough has already been said to make it quite clear 

 that many of the parts of Corymorpha are quite indepen- 

 dent of the rest of the polyp in their capacity to respond 

 to stimuli. Thus the stalk of Corymorpha will shorten 

 and even localize a stimulus applied to one side of it with 

 as much success after the hydranth has been removed 

 from it as when the polyp is completely intact. There is, 

 therefore, no reason to suppose that the hydranth con- 

 tains nervous centers that are in any way essential to 

 these responses. 



In a similar way the separated hydranth exhibits on 

 stimulation movements in its distal and proximal ten- 

 tacles and its proboscis that are in all respects counter- 

 parts of the movements of these organs in the polyps as 

 a whole, showing that the hydranth is in no sense depen- 

 dent upon the stalk for its neuromuscular activity. The 

 separate hydranth as well as the separate stalk can be 

 anesthetized with chloretone or magnesium sulphate, 

 and, after having thus lost their responsiveness, these 

 parts will separately recover when placed in pure 

 seawater. 



When the proboscis of a Corymorpha is cut off, the 

 attached distal tentacles continue to exhibit spontaneous 

 movements and turn vigorously away from the mouth on 

 stimulation as they do on the intact animal, activities that 

 they lose temporarily on anesthetization. The proximal 

 tentacles also exhibit great independence. If one is cut 

 from a hydranth, its curved form brings it to rest on the 

 bottom of a glass vessel on its side and it is compara- 

 tively easy to determine by the direction of its curve 

 which is its oral and which its aboral face. On stimulat- 



