IV 



PHYLUM CCELENTERATA 



127 



which the whole tentacle can be retracted. At one pole, the 

 oral, is an opening, the mouth : and at the opposite pole are 

 a pair of minute pores, the excretory pores, which are the 

 openings of a pair of canals given off from the enteric cavity. 

 Between the two excretory pores is a remarkable structure, 

 which is the nerve-centre as well as an organ of special 

 sense. The mouth leads into a flattened tube, the gullet, 

 and this again leads into a cavity, the infundibulum, which 



ad.c 



\-nu- 



-sc 



FIG. 62. Hormiphora plumosa. A, transverse section of one of the branches of 

 a tentacle ; B, two adhesive cells (ad.c.) and a sensory cell (s. c.) highly magni- 

 fied, cu. cuticle ; me. nucleus. (After Hertwig and Chun.) 



probably corresponds to the stomach of the Sea-anemone. 

 From this certain canals are given off. 



Stinging-capsules are not developed, their place being 

 taken by a number of peculiar cells called adhesive cells, with 

 which the branches of the tentacles are covered. An 

 adhesive cell (Fig. 62, B} has a convex surface, produced into 

 small papillae, which readily adheres to any surface with 

 which it comes in contact, and is with difficulty separated, 



