324 . G. H. PARKER 



will retain this bent form for at least twenty minutes. I, there- 

 fore, believe that the axial cells have the character of a plastic 

 skeleton, as in fact Torrey ('07, p. 201) has stated, and that 

 they will take a certain amount of set, from which they are not 

 quickly and easily freed. This set may be due to the molding 

 effect of the musculature or to changes in their turgesence or to 

 both. In this respect they seem to me to be important adjuncts 

 in the geotropic responses of Corymorpha. These responses, 

 however, are accomplished primarily by the neuromuscular 

 apparatus (Parker, '17 a), as has been shown by Loeb ('95) for 

 Cerianthus. 



7. FEEDING 



If the contents of the digestive spaces in Corymorpha are 

 examined, they are found to contain, as Torrey ('04 a, p. 397) 

 has observed, organic detritus composed of the remains of cope- 

 pods, rotifers, diatoms, and various chlorophyl-bearing pro- 

 tista. The cavity in which these partly digested materials 

 circulate is by no means simple. Its extent and ramifications 

 can best be made out by the injection into it of india ink under 

 slight pressure. In this way it can be demonstrated that the 

 body of the hydranth including the proboscis contains a con- 

 siderable gastro vascular cavity (May, '03, p. 585). Extensions 

 of this reach out into the peduncles carrying the medusae but 

 not, so far as I can ascertain, into the tentacles. Proximally 

 the gastrovascular space contracts into a central tube as it passes 

 from the hydranth into the stalk, at the distal neck of which it 

 connects with the dozen or more longitudinal canals which 

 extend in some what parallel courses proximally through the 

 more peripheral layer of the stalk well down to its buried end. 

 These tubes show not infrequent anastomoses, especially in the 

 proximal portions of their course. The injection of the whole 

 gastrovascular system is best made by cutting off the proximal 

 tip of a polyp, inserting a cannula in among the vacuolated cells, 

 and after tying it in that position, slowly injecting india ink 

 under slight pressure. The ink quickly makes its way into the 

 canals and flows forward freely till the neck between the stalk 



