500 Howard Edwin Enders. 



the neuropodia. The neuropodia transfer the foreign matter back- 

 wards from one pair to the next and thence, by extension of the body, 

 push it to the exterior. During this process ten or more of the pos- 

 terior segments are pushed beyond the orifice of the tube. When the 

 foreign matter is not expelled on the first trial the movements are 

 immediately repeated. After all of the irritating material is expelled 

 the worm takes its normal position in the horizontal portion of its 

 tube and maintains a continuous current of water as it did before 

 the diatoms were added. 



Chsetopterus may reverse its position in the tube. This is done 

 while the animal is in the horizontal portion of its tube. The ventral 

 lip of the buccal funnel and all the segments back of it successively 

 bend ventralwards and then the whole body moves as though over a 

 pulley situated at this point until the animal is reversed. This 

 would bring the ventral surface of the animal uppermost if it were 

 not righted by a twisting movement of the anterior region as soon 

 as it has been turned under. All the remaining portions of the body 

 are then righted in natural order. When the animal has reversed its 

 position, the sand, which is then beyond its posterior end, is expelled 

 from the tube as has been described above. 



The reversal of the current of water follows the reversal in the 

 position of the worm. I have seen this reversal occur twice within 

 an hour in the glass tubes of my aquaria. It is done in from ten 

 to twenty seconds. It may be induced repeatedly by introducing a 

 large amount of sand into the incurrent orifice of the tube. 



The animal generally lies in the horizontal portion of its tube, 

 but it may protrude its proximal or distal end at the orifices when 

 it removes objectionable matter and when it repairs or rebuilds 

 the vertical arms of its tube. In all respects, in so far as I have 

 been able to observe, the animals on the shoals, and the two living 

 individuals which I have had under my observation more than nine 

 months in an aquarium, in the laboratory of the Johns Hopkins 

 University, behave like these in the glass tubes. 



Even if the uncinal plates of the internal and external lobes of 

 the neuropodia or' their modifications, are used exclusively for "hold- 

 ing to the wall of its parchment tube," it i? clear that the animal 



