OBSERVATIONS ON POLYZOA. 205 



crown. This is perforated in the centre by the round 

 mouth, overshadowed by the tongue like Epistome (PI. 7, 

 fig. 5, I', I"), which is an obtuse, upward fold ofthelopho- 

 phore, opening below into the neural chamber, or cavity. 

 This cavity contains the orbicular nerve-mass suspended 

 immediately under the epistomic opening (PL 7, fig. o, S). 



The surface of the tentacles, the oral side of the epis- 

 tome, the lophophore and the interior of the throat in the 

 vicinity of the mouth are covered by cilia (PL 7, figs. 4, 

 H, 5, H' ; ). Constantly vibrating towards the centre of the 

 crown, these cilia create a vortex in the water, at the apex 

 of which lies the mouth, always open and ready to en- 

 gulph the microscopic plants, or Infusoria}, that may be 

 caught by the encircling current, and swept into this liquid 

 trap (PI. 7, fig. 5, I"). 



The polypides not unfrequently form a sort of cnge, by 

 interlacing the extremities of their tentacles, and imprison 

 the more active of the Infusoriae, who would otherwise 

 readily escape. Thus inclosed, however, their strength is 

 expended in fruitless efforts to break through the tentac- 

 ular bars, until finally exhausted and overcome, by the 

 power of the miniature maelstrom, they are whirled unre- 

 sistingly downward into the funnel shaped throat. 



The tentacles are used not only, as above described, to 

 catch the prey, but for a multitude of other offices. They 

 are each capable of independent motion, and may be 

 twisted or turned in any direction; bending inwards, they 

 take up and discard objectionable matter, or push down 

 into the stomach and clear the oesophagus of food too small 

 to be acted upon by the parietal muscles. They are also 

 employed offensively in striking an intrusive neighbor, and 

 their tactile power, sensitive to the slightest unusual vibra- 

 tion in the water, warns the polypide of the approach of 

 danger. 



Between the lophophore and the ccenoecium, the internal 

 organization is plainly seen, the pellucid wall of the tube 

 offering no obstacle to the eye of the observer. 



The alimentary canal hangs from the lophophore, occu- 

 pying the centre of the polypide, and floating freely in the 

 rapidly moving blood. The yellowish oesophagus, the 

 stomach barred with brown, and the brownish intestine 



ESSEX INST. PROCEED. VOL. IV. A A. March, 1866. 



