52G Howard Edwin Enders. 



higher and again withdrew. This action was repeated five times in 

 extending the rent, seven millimeters, to the end of the tube. The 

 rent was produced by means of the expansion of the muscular, setig- 

 erous region and not by the sharp lance-shaped setae as one might 

 suppose. The rent occurred in a position ventral to the plastron. 

 ^^'hen the tube w-as split to its extremity the worm thrust one side 

 of the anterior region through the cleft and removed the sand about 

 it by means of its setigerous notopodia. They pressed a portion of 

 the sand aside, but some was removed backwards into the tube and 

 later discharged at the other end. 



AVhen the tube was split to its end the worm spread the basal por- 

 tion 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 seconds, then withdrew 

 into its tube for half a minute, after which it took a position a little 

 nearer to the orifice of the tube. The performance was repeated till 

 the edges were reunited by a wedge-shaped insertion of parchment 

 that widened to three millimeters just below the level of the sand. 

 I could not determine which region of the body was most active in 

 the secretion of the mucus, which becomes parchment-like, but I 

 observed that it was shaped by the lower lip of the buccal funnel, 

 and that the parchment film had advanced a little higher each time 

 the animal applied its ventral lip to the cleft. The splitting of the 

 tube and the closure of the rent were completed in thirty-five minutes. 



The splittings occur indifferently on any portion of the circum- 

 ference' of the tube, but they are found chiefly on the upper side of 

 the horizontal portion. When they are extensive it is indicated by 

 the abundance of sand discharged at long intervals from one arm of 

 the tube. I have found some large tubes which had strips of thin 

 parchment two centimeters Avide and as long as the horizontal por- 

 tion of the tube. 



The new portion of the wall is thin and membranous at first and, 

 M'hile it becomes thicker with age, can be observed, long after its 

 formation, as a strip somewhat thinner than the remaining portions 

 of the wall. Its inner surface is smooth, like the inner wall of the 

 oth(n' portion, and its outer surface is similarly covered with sand. 



