132 



exiiMiult'd the lirst pair of setigeroiis somiiruts and split the tube longitudi- 

 nally at its outor sidr. tluMi witlidrew quic-kly into tlic docjji'r i>ortion of the 

 tube. Fifteeu ov twenty sin-onds lator tlu' worm ivapiH-ared at the level of 

 the sand, extended tlie n>nt a little liigher and witlidrew. This action was 

 repeated tive times in extending the rent, seven nuilimetevs, to the end of 

 the tube. The rent was produced by means of tlie expansion of the mus- 

 cular setigerous region and not by the sliai'p lance-shaped setae as one 

 might suppose. The rent occurred in a position opposit*> the ventral sur- 

 face of the body. When the tui)e was s^ilit to its extremity the worm 

 thrust one side of the anterior region through the cleft and removed the 

 sand uliout it by means of its setigerous notoiiodia. They pressed a portion 

 of the sand aside but some was removed backwards into the tube and later 

 discharged at the other end. 



When the tube was split to its end the worm spread the basal portion 

 of the rent by a slight expansion of the ventral side of its lower lip and 

 the foremost portion of the anterior region. The worm remained in this 

 position for fifteen or twenty sec()nds then \\ itbdrew into its tube for a 

 half minute, after which it took a position a little nearer to the oritice of 

 the tube. The performance was repeated till the edges were reunited by a 

 wedge-shaped insertion of parcliment that widened to three millimeters 

 just below* the level of the sand. I could not determine which I'egion of 

 the body was most active in the secretion of the mucus, which becomes 

 parchment-like, but I obser^■ed that it was shaped by the lower lip of the 

 buccal funnel, and that the jiarchment film had advanced a little higher 

 each time the animal applied its ventral lij) to the cleft. The splitting of 

 the tube and the closure of the r«Mit \vert> completed in thirty-tive minutes. 



The splittings occur indifferiMitly on any portion of the circumference 

 of the tube, but they are found chietly on the upper side of the horizontal 

 portion. When they are extensiv(> it is indicated by the abundance of sand 

 discharged at long intei-vals fi'oni one arm i>r the tube. 1 have found some 

 large tubes that had strips of thin parchment two centimeters wide and 

 as long as the hiuMzontal portion of the tube. 



The new ]tortion of the wall is thin and membranous at first and. while 

 it becomes thicker with age. can be observed, long after its formation, as a 

 strip somewhat thinner than the n'maining portions of the wall. Its 

 inner surface is smooth. like the inner w.-dl of the other i)ortion. and its 

 outer surface is similarly covered with s.uid. 'I'he wide, horizontal portion 

 of nearly every tube bears one or more of these strips inserted lietween the 



