FOOD AND THE NEEVE-NET 141 



that the body of a Metridium could contain can be passed 

 through its oesophagus, and yet the ciliary reversal is as 

 effective after this period of continuous feeding as before. 



Other evidence of the relative independence of the oral 

 cilia as compared with other effectors is well seen in speci- 

 mens of Metridium that have been narcotized with chlore- 

 tone, by which all nervous activity is abolished. A piece 

 of food placed upon the tentacles of such an animal calls 

 forth no special response and either remains where it 

 was placed or moves sluggishly off to the periphery of 

 the disc under the action 'of the tentacular cilia. When, 

 however, such a piece is put on the lips, the cilia reverse 

 and the morsel is gradually carried down the oesophagus 

 and discharged into the digestive cavity. The swallowing 

 is usually not so rapid as in the normal animal, for, under 

 this form of narcotization, the transverse muscles of the 

 mesenteries do not respond to the food by opening the 

 oesophagus and consequently the cilia are obliged not only 

 to transport the morsel but to force it down a partly 

 closed tube. This, however, they are usually able to do, 

 and thus, quite independent of neuromuscular help, they 

 bring about the swallowing of food and the rejection of 

 non-food, for under these circumstances inert materials 

 were found not to reverse the ciliary stroke. Thus, as 

 Allabach (1905) has pointed out, the reversal of the ef- 

 fective stroke of the oral cilia is a process that is largely 

 independent of the physiological state of Metridium. 



In one particular only does this process appear to be 

 related to the general condition of the animal. Ordi- 

 narily the reversal of the oral cilia is accomplished by 

 dissolved substances from the food, and in the earlier 

 studies on this subject in Metridium this was believed to 

 be the only way by which such reversal could be induced 



