Chgetopterus Variopedatiis. 497 



Habits and Physiology. 



Generally speaking, Chsetopterus remains wholly confined within 

 its dark brown, parchment-like tube which is embedded in the sand. 

 x\lthongh confined within a tube it is not as inactive as its condition 

 would suggest. So long as the tube is submerged in water and the 

 animal is undisturbed it usually keeps a more or less constant cur- 

 rent of water traversing its tube. The water serves the double pur- 

 pose of aeration and of bringing in the supply of food. 



The force wath which the water is discharged from the tubes of 

 an average size worm is quite considerable. On the shoals I have 

 frequently dropped a pipette full of sand into the incurrent end 

 of the Chsetopterus tube before the shoals were completely uncovered. 

 The current ceased almost immediately or was weakly reversed, and, 

 at the end of about a half minute, the animal suddenly expelled the 

 w^ater with such force that it carried the sand to the surface of the 

 water thirty to forty-five centimeters deep. When a larger amount 

 of sand was dropped into the tubes it was expelled after a minute 

 or more. Under these conditions the animal reversed itself in the 

 tube as wall be described in a succeeding paragraph. 



Through its whole life Chsetopterus lives within the same tube 

 or enlargements of its tube, but I cannot agree with Laffuie that 

 "il ne se montre jamais a Vexterieur de son tube." I have fre- 

 quently seen several segments of the distal end of the worms pro- 

 truded from the tubes in my aquaria and on the shoals. Two adult 

 specimens that I collected during the summer of 1905 gave evidence, 

 by their regenerating posterior region (in one, all segments back of 

 the third; in the other, a large individual, all the segments back of 

 the fifteenth), that they had protruded a portion of their body at an 

 unfortunate moment. A portion of the "tail" is sometimes exposed 

 above the orifice of the tube when a large quantity of sand, or other 

 irritating matter that has been carried into it, is partly SAvept and 

 partly pushed out. I have several times seen five or more segments 

 pushed out of the tube and then again withdrawn. This was observed 

 on days when the sand of the exposed shoal had become excessively 

 heated near midday. 



While it is quite common to see the buccal funnel just touch the 



